This is a ballot box I designed. The design goals were as follows:

• simple
• secure (as in: cast votes should be hidden and unreachable unless the box is opened)
• no screws
• easily disassemblable and reassemblable (no glueing/fixing)

I came up with a design where…

• the bottom is held in place by the sides;
• the sides are held in place by the front and back;
• the front and back are held in place by the top;
• the top is held in place by a single padlock.

Nifty!

With the padlock in place, access to the interior is possible only via the top slit (or by applying brute force to the box ;-) ). Removing the padlock, the top can be slid back and opened. Now it is possible to slide up the front and back, allowing for the sides to be thus removed. Works like a charm!

I believe to have reached all the goals I set, except for the swivel-mechanism: I have glued it together after all. (Using a double-wall for the sides might solve this issue, but then again assembling would be a pain…) I can live with this compromise, since even so, when disassembled, the ballot box can be safely stored in a convenient manner until the next time we might need it.

First test was small-ish; the big one is the one I actually use.

I used 5mm beechwood (it's more like 4.65mm but that's even an advantage since the rather big surfaces tend to bend a bit on natural wood, making the tolerances a pain—a little wiggle room goes a long way).
When upscaling to the final size, I optimized the design so as to make as much use of the 100x60cm sheets of material I had available: 1 ballot box = 1 sheet. The box needs to be able to accommodate ~200 votes, the size turned out to be just right.