Step 1: Find Reclaimed Wood for the Deck

In my case, I found a broken table discarded on the side of the road. :) The table top was a bit thick, but it was the perfect starting point for the skateboard.

Step 2: Create a Cardboard Prototype

Using a big piece of cardboard or paper, plan out the shape and dimensions of your board. It helps to put it on the ground and make sure it's a good size for your feet
Trace an outline of the paper prototype onto the surface of your wood (soon-to-be skateboard deck)

Step 3: Shape Your Board

Use a vertical band saw to cut around your skateboard outline
Next, the table I used for my skateboard was thicker than I wanted. If this is the case for you too, you can use a plane to reduce the thickness of your board
Smooth the edges. I used a belt sander to round the edges of the board (all around the top and bottom), as well as to smooth the surface

Step 4: Drill Holes for the Trucks

Line up the trucks on the board where you want them
[Note: if you want to be able to kick up your board from the back, make sure not to put the back truck too far back. Mine's far enough forward where I can still step on the back of the board to kick it up.]
Mark the location and drill holes. Countersunk works best so the top of the screws are flush with the surface of the deck

Step 5: (optional) Coat in Epoxy & "grip Tape"

I coated my board in epoxy to make it more durable. But the epoxy make it pretty slippery, so I topped it off with "grip tape" made from sand!
While the epoxy on the top side is drying, sprinkle a thin layer of fine sand all over the board. A cheese grater or strainer is a great tool for this and distributes the sand evenly. Practice and figure out a good technique before applying the sand on the epoxy though - you only get one chance!
Once the epoxy's dry, you may need to clean up the drill holes to get rid of any excess resin. It helps to try and cover / block the holes while applying the epoxy