My garden bed was 2' wide, 10' long, and 22 inches high. This is what space I had available that got full sun in my backyard. Be careful if you are making it along a fence that it is not too wide - you want to be able to easily reach the back of it to tend it and harvest.

I generally followed the instructions on Albo Pepper's website.

Here is a link to his video on how to make a SIP bed.

Supplies

Tools

Drill
Impact driver (recommended)
Staple gun
Hammer
Corner square
Level
Kreg Jig (optional)

Materials

Deck screws - 1 box. (2.5 inch length with star bit recommended)
4 x 2 by 10 by 10' long boards
1 x 2 by 10 by 8' long board (sides)
3 x 2 by 4 by 10' boards
1 x 2 by 4 by 8' board
Stain (optional)
Wood sealant (optional)
Large roll of thick plastic. I got .6 mil, but suggest you get a pond liner instead.
Perforated corrugated pipe - 4 x 10 ft lengths
Poly tubing, 8 inch length - 1/2 inch width.
PVC tube, 1/2 inch width, the length should be the finished height of your garden bed

Wicking Soil Mix

Peat moss - 1 bale
Perlite - 1 large bag
Vermiculite - 1 large bag

Potting Mix to top off bed - Approximately 6 x 2 cu ft bags.

I did not get pressure treated lumber for 2 reasons:

The inside of the bed is lined with plastic so it doesn't need weather protection.
The outside of the bed was stained and clear coated.

Step 1: Cut the Lumber and Stain

I cut 1 of my 2 by 10's to 2 foot lengths for the sides of the bed. I used my 8.5 inch miter saw because that is what I have. Do not cut the 2 by 4's at this point because you don't know the length yet. They can be stained now though.

Then I stained the 2 by 10 pieces on 1 side and on the edges. I chose a solid stain by Behr in the color Wood Chip.

Lastly I applied a clear wood top coat on the stained surfaces. Just for added protection.

Step 2: Begin Assembly

I used my 4 by 4 fence posts as the supports and means to level the back boards.

***Make sure your ground is level under this box. If it is not I would highly recommend building a bottom panel***

Once they are level, screw your pilot holes and screw them in. Do pilot holes for all of the screws so that your wood doesn't split, which would let in water, pests, and can warp the wood over time.
Once the back it built I added the sides, use the corner square here. I used a rock or piece of wood to hold the board at the right height while I was using the drill.
Add the middle support boards onto the back and front panel. We will tie them together later. I left my supports off the bottom 5 inches so that the tubing could go underneath it.
Finish adding the sides and then do the front panels the same way. I butted the end of my 10 foot long boards into the side panels, because the tubing is 10 ft long. You don't want do the butt joint the other way, because then the side panels would reduce the bed's overall length. by 2 inches on either side. Then you would need to trim the tubing by 4 inches.
Again ensure the ground under your bed is level after it is done being constructed. I added mulch to help with my sloped yard. If the bottom isn't level, the water is going to be distributed unevenly among your plants. Its worth it to make sure this is correct now.

Step 3: Install Lining and Insert Tubes

Staple on plastic lining, as one continuous piece. I highly recommend folding edges over and stapling through them for stronger, -smooth edge.
In the corners, gently push the lining into the lowest point, and create a triangle with the excess.
Then tuck the triangle behind another side of the lining. Try going in the same direction for all 4 corners. My lining was lighter color so I could see the triangle, hold it in place and staple it in. Use a hammer to push any staples that didn't completely set in. If you supports are already in place just staple around them.
Keep everything flush and smooth. Pockets or ripples can collect water or soil, you want your plants to be able to reach straight down and pull up the water from the reservoir.
Insert perforated tubing, you want very little room on the sides. Maybe 3 inches on the sides combined. My tubing has landscape fabric on the ends tied on with string, this is not required but I had the materials already so I did so.
Add center support, cut to width of bed and screw into 2 middle supports.

Be careful not to rip the lining!!!

Step 4: Add Overflow Tube and Wicking Material

Add Overflow Drain - for when it rains excessively so your plants don't drown!

Lift up one of the inner tubing pieces and mark a spot to drill
You want the hole to be within the inner tubing, near the top edge. Drill through the inside to the exterior of the bed. I added one overflow to each side of my bed.
Add overflow tube, of 1/2 inch poly tubing, a 4 inch length worked for me. Make sure it reaches inside of your corrugated tubing within the bed.

Mix up the wicking material

Mix equal parts peat moss, perlite and vermiculite. Mix by hand until it looks like the photo.
Pour on top of tubing.
Stuff into spaces in between tubing and sides of the bed so it is snug.
Level off the surface for the next step

Again I followed the guidelines on Albo Pepper's website.

Step 5: Add Fill Tube and Soil

Before the soil is added, screw or cut a small hole in your perforated tubing.

Insert a length of PVC into this tube. I used 1/2 inch because it was easy to fit a soda bottle onto as a funnel. Cover your fill tube so it doesn't get clogged with soil as you fill up the bed.

Now add the soil! I used:

Miracle Gro Moisture Control 2 cu ft bags (75%)
Cypress wood chips (10%)
Perlite (5%)
Vermiculute (5%)
Worm Castings (5%)

Again I followed the guidelines on Albo Pepper's website. Fill it close to the top edge of the bed. It will sink down with watering or a of couple rainy days.

Step 6: Plant It Up!

I used the square foot gardening method and lightly scored the dirt at 1 foot lengths.

Then dug holes for my transplanted tomatoes and peppers. You can do this step before or after adding the edges to the bed. I needed to plant mine ASAP.

Step 7: Add the Edge or Frame to the Top

Use your 2 by 4's to cover the top of the bed and give it a finished look

Attach the 2 longest lengths first. I have mine overhang into the bed 1/2 inch. I screwed them in the middle, and 2 foot increments either direction.
Now measure the length between your 2 edge boards. This will give you your custom length to cut the side edges. Mine was 27".
To prevent the corners from splitting and having 2 screws close together, I used the kreg jig on the underside of the side pieces.
Then for the side pieces, put 1 screw in the center, and then use the kreg jig screws underneath to create a tight, seamless bond.
Touch up and spots or cut ends with stain if needed.

Step 8: Optional - Add String Supports to Keep Plants Upright.

Cut wedges, any angle works as long as one edge has a 90 degree angle. Mine were leftover pieces from the miter saw.
Screw pilot holes into wedges. Direction doesn't matter, but you should decide if you want it going into the top board, or the side. Mine goes into the side - the fence post.
Install top board onto the fence post, and wedge underneath.
Lastly add the 10 ft board along the top edge. Screw into support board underneath. I put mine directly over my tomato and pepper plants.
Tie string at 1 ft increments and have it hang down to the garden bed soil. Use knots, because the plants weight will pull on these.

Support plants

Tie a loop under plants stem - make it a loose fit for stem growth.
Either wrap around stem gently or:
Purchase greenhouse clips which grab string and snap around stems. This is what I used. You can see this pulled my tomato plants off the ground.

I used this method because with this type of bed, you can't add a thick stake or cage around your heavy plants. It could very easily puncture the lining and let the water leak out of the reservoir. The clips that I got are very inexpensive and have a strong grip.