Here is a list of tools and materials you will need:
1/2 birch plywood 2x2 ft
1/8 birch plywood 2x2 ft
small 1 inch finishing nails
snare drum snare wire (found at most music stores) http://images.guitarcenter.com/products/optionLarge/Puresound/DV016_Jpg_Large_1274034479841_A.jpg
orbital sander or just something to sand the wood
stain of your choice
some kind of tung oil or varnish to protect the wood
4 small 1 inch bolts with flat tops that will fit through the snare wire holes
4 washers and nuts
a jig saw to cut a hole in the wood
Step 1: Cut the Wood Into Needed Sizes
Two 18 1/2" x 9 1/4" 1/2 in thick boards
Two 9 1/4" x 8" 1/2 in thick boards
Two 18 1/2" x 10 1/8 " 1/8 in thick boards
Make sure that each identical pair of boards is flush when lined up so that they are equal in size.
Step 2: Cut the Resonance Hole
Step 3: Prepare the Box
Step 4: Attaching the Snare Wire
and mark where the ends of the snare wire are and where the holes are (it is important to make these marks about 1cm wider than the actual snare wire because the snare will need to be stretched in order for it to stay tight against the playing surface). now simply drill the holes and fasten one side of the snare wire with bolts washers and nuts, then while stretching the other side with pliers, put it on the bolts and fasten it down. You can tape it to the board with a few pieces to eliminate any ringing when u play it later.
Step 5: Finishing the Cajon
Once dry, Your cajon is ready to play! Enjoy!