CHECK YOUR LOCAL LAWS REGARDING COLLECTING BEFORE YOU PICK ANYTHING! Get proper permits etc.
Basically, I made two identical, incredibly simple frames.
Unfortunately, the first one I made wouldn't fit into a backpack for our collecting trip. It was 16" by 22".
The instructable photos document the building of the extra large version. The photo below is the finished project - It is 11" by 16 ". Same wood, same weight as the larger version (because I overdid it on the number of boards I used!). If I had to do it again, I would use ChrysN's Pocket Flower Press instructions http://www.instructables.com/id/Pocket-Flower-Press/, but make it larger and drill holes in the top and bottom pieces of wood to lighten the load and allow for air circulation..
Step 1: Materials
I used 1/2" x 2" boards but herbarium presses that are being sold use 1/4" x 1" boards. It would sure cut down on the weight, especially if you are planning on taking it on collecting expeditions. The thicker boards are very sturdy though.
You will need about 18 feet for a 11" x 16" press. (Width times 10 plus length times 8. For a 11" x 16" press, you would need 110" + 96" = 206" or or just over 17 feet. Say 18 feet to allow for waste from cutting and different board lengths.
Saw I'm lucky enough to have a radial arm saw, which makes cutting the boards quick and accurate. A hand saw would work fine.
Wood glue This is what is going to hold your boards together.
Finishing Nails (or whatever you have on hand) To hold the wood frame together while the glue is drying. They should be long enough to go almost all the way through two boards, flat side to flat side.
Straps I bought two band clamps from the hardware store. These will be used to tighten your press as your plants dry.
Carpenter's square I skipped using this the first time and ended up with my two frames not matching up and had to start all over.
Newspaper To separate your specimens and to absorb moisture. Blotting paper works as well.
Corrugated Cardboard To separate your specimens and to allow for air circulation.
Step 2: Prepare the wood. Cut to size.
Cut 8 pieces of wood based on your finished length measurement.
Separate into two piles: 5 short pieces with 4 long pieces in each pile.
Step 3: Put your Frame together
You can either do one frame and then make the other or double the steps described below and make two frames at the same time.
Step One: Take one long piece and one short piece and lay one on top of the other so one end of each board is square to the other.
Step Two: Generously apply glue to each board where they will be overlapping and making sure the corner is square, hammer one nail to connect the boards. The boards may slip when you are hammering but with only one nail in, you should be able to adjust the corner to make it square. Use your carpenters' square.
Step Three: Hammer a second nail in to secure the square-ness.
Step Four: Repeat Steps One through Three with another long piece and short piece.
Step Five: You should have two "L" shapes. Arrange them into a Rectangle (long side parallel to long side, short side parallel to short side). Apply glue to the unattached corners and hammer one nail to connect each corner. Again, check to make sure your corners are square before hammering in the second nails.
Step Six: Wipe off excess glue.
(You would think that two L's that were square would automatically make you a nice rectangle, but it didn't work for me.)
Step Seven: Eyeball estimate the middle of each of the long boards of your Rectangle. Generously apply glue at the middle of each side and nail one of the remaining short boards in place. Again, start with one nail, make sure the board is positioned in the right place, then hammer in your second nail.
Step Eight: Eyeball estimate the center of the space between the end short board and the middle board you just nailed in place. Generously apply glue and following the instructions above, nail in place. Repeat for the other side. Now you have a Ladder.
Step Nine: Wipe off excess glue.
Step Ten: Flip your Ladder over so the short boards are at the bottom.
Step Eleven: Visually divide the space between the parallel long board into thirds. Apply glue, and nail the last long boards into place.
All done...with one side (unless you were doing two at once.)
Step 4: Cut corrugated cardboard and insert newspaper
Get newspaper and keeping it folded, place the sheets between the cardboard. I used multiple sheets to absorb the moisture from the plants.
The newspaper doesn't have to fit perfectly. Just be careful when you put your plants between the pages that parts of them are not sticking out beyond the edge of the frame. These parts won't flatten and probably will get damaged.
Step 6: Plants in Press
After bringing the filled frame home, we neatened up the stack but I forgot to take pictures. So sorry.
You should check the straps and tighten them every day because they may loosen as the plants dry and shrink. Also, flip the frame over so air circulation is more even.
See the pictures on the mechanics of the tightening of the straps. They can get EXTREMELY tight!
There are many botanical herbariums that have guidelines and instructions on how to mount plant specimens. Check them out!
Can't wait for the next expedition!!