Q&A for How to Build a Cajon

Any "big box" hardware store (i.e. Home Depot or Lowe's) will have both 1/8" and 1/2" plywood in various sizes. Neighborhood hardware stores are not likely to have all the plywood that you need.

Yes, absolutely correct! Of course, you will need to employ the proper striking techniques to really get the most out of those sounds, but that's the main idea of it.

Yes. However, keep in mind that adding paint might change the sound because of its weight and structure.

If you want to attach a snare, attach guitar strings on the back side of the front head, stretching them so they are tight against the back panel.

5 of the 6 sides are all made of the same 1/2" plywood. This includes the back of the instrument. The only bit made of the thinner sheet is the tapa (the part you strike).

Any plywood will do, but I would recommend using cabinet-grade plywood (birch, oak, maple...) as those will look nicest when finished.

If you want to attach a snare, you will simply attach guitar strings on the back side of the front head, stretching them so they are tight against the back panel.

Yes, birch plywood takes stain quite well, just make sure your stain and final finish are compatible.

The tapa is the thinner wall that you strike. The hole is in the back (though I've also seen it on the side in some variations of the design).

You can use wood and screws, or build a small frame and use finishing nails. My professional cajon uses a frame with some finishing nails in it.