I designed a simple shape box for my soon-to-be two-year-old child. The lid can be opened by just sliding it, and it contains four different basic shapes, which is enough to give that shape-obsessed girl a break from all the memes. If you need to make simple modifications, like adjusting the depth of the box, I've already included the basic Blender files.

Basic printing settings. No support is needed. You may need to increase the temperature of the heating bed to 70 degrees Celsius to prevent the edges from curling up.