I started with cutting the sides and top/bottom out of some Baltic Birch plywood that I had laying around the shop. BB is very solid and dense, which I hope is a positive with a resonance chamber.

The bottom is 12mm (1/2") thick, but I had enough 19mm (3/4") for the other 4 sides. Since you sit on the drum to play it, I wanted it to be pretty solid.

The front - the Tapa - is another matter. This is supposed to be 1/8" plywood. It needs to be nice and thin, kind of like a drum skin, I guess, since that is what you hit. I happened to have a scrap of oak door skin which my dad gave me last summer, which was exactly what I needed. The artist in me was glad that I had something that was NOT the same colour as the rest of the piece.

On the router table I ploughed rabbets along the back edges of the sides, to hold the back of the Cajon. I also ploughed shallow rabbets around three sides of the top and bottom (not the front side) so that they would lock onto the sides nicely.

The sides and back were all glued and clamped together. No nails -- Baltic Birch plywood takes glue very well, even on the edges.

All the joints were then reinforced from the insides by gluing blocks along the inside corners. (Somewhat unimaginatively, these are known as "glue blocks".)

I drew a 6" diameter circle towards the top of the back, and used a drill + scroll saw to cut that out. I rounded over the edges on the router table before attaching it. This is needed to let the sound out. It also serves as a handle for carrying, so you really want it smooth and rounded for comfort.

I then aggressively rounded over all the outside edges with a roundover bit on the router table.

I like the adjustable snare on the two Cajon drums which I linked to above (Steve Ramsey's and Serge Duclos'). However, I did not want any external knobs or anything else like that on mine. I wanted a clean and smooth exterior. For one thing, I like the look. For another, the resulting smooth sides make it a bit easier to pack on a shelf for storage. (I was also making this project as much from available materials as possible, so I was not going to go out to buy hardware.)

As I was browsing different websites, and checking out different Cajon pictures, plans, descriptions... I came across the Sela kit, as mentioned above. They had a removable snare in their kit, which I found interesting. Based partly on that, I came up with this: I would make a pair of notched pieces to go on either side of the drum, about 1/3 of the way down from the top. Into that would go a block on which I would mount the snare wires. This could then be removed if you wanted to play without the snare. This is a pretty simple design, so if I don't like something about it, we can fairly easily make changes. Remember, this is my first Cajon!

Testing out how a block fits into the notch I cut on the router table.

I ripped a piece of scrap pine at an angle for mounting the snare wires. I want them angled toward the tapa so that they lay against it.

Here is the snare block. The piece of angled pine is mounted here, and the two bits of the snare are mounted on it. This is how it will be mounted in the drum, so that the wires press against the tapa.

The snare was my only expense on this project. I picked up a drum snare kit for about $10 at a local music store. It was then cut in half, and the two halves are mounted as shown here.

(And yes I realize that it is not quite correct to say this is the "only" expense. After all, I did pay for the plywood at some point in the past. But that was paid for long ago, so it feels like free wood now! )

This illustrates how the snare block is mounted inside the Cajon. The tapa is then attached to the front over top of this.

Here is a closeup showing one of the snare block mounts. Note that it is set just a bit back of the front edge, so that it should not be touching the tapa. We don't want it affecting the sound.

Here the tapa is attached so we can hear it for the first time. Seems to work!

I then removed the front for finishing. I applied one coat of sealcoat shellac to warm up the colour of the pale wood. This also raises the grain, so a very light sanding with 400 grit paper follows. Two coats of Varathane were then brushed on.

All projects get signed and dated in an inconspicuous place.

I mounted some self-adhesive rubber feet, but added a screw to each foot also, as insurance.

You don't need to remove the tapa to access the snare. The rear hole is just big enough that you can reach your arm in, pop the snare block up and out of it's mounts, and then work it out of the hole.

And finished: Rear and side view.

Finished: Front view.

Here is one final design note. I read a few websites where the tapa is glued to the case, but most others recommend that you fasten it just with screws. This means it is removable to access the insides, and also that supposedly helps with the sound. On this drum, this also lets us create a "slap" corner. Note that there is NO screw in either of the top corners. Those are left loose on purpose. You can slap/tap in the top corner and you the tapa will vibrate against the corner giving a slap sound. This is adjustable by sanding back the front face of the Cajon. I left it as is, and it sounds pretty good to me, but on the Lee Valley plan, for example, they recommend sanding back the corner approximately 1/16th of an inch (1.5mm).