For kids you might want to do something to keep the top attached to the box - otherwise they'll lose it. On the slide top you could glue a piece into the top of the box (the inside of the sliding part) that hits the box side when slid open.
Here's a box that is a kind of ring cut made from a 2x4. You can probably see how it is cut from the photo. It takes no joining - just cut the 2x4, glue on a thin top & bottom (these are 1/8" BB Ply) and shape the fixed part so there's no interference. Then pin it with dowels or small nuts & bolts.


Here's a regular ring-type box, but the top comes off so it might get lost. The rings are 1/4" thick. It's cut from a 1x4 - any length you need. A 2x4 could be used if you want it deeper.
