I recently made a custom box for a card game called frantic:https://www.thingiverse.com/thing:4123355
I liked the design of the box so much that I made it as an OpenSCAD version that is now fully customizeable !
The lid is held shut by the inbuilt latch and when creating you can choose either inside or outside dimensions depending on your needs.
It needs 2xM3x25mm bolts to secure the lid and thats it.

Update:
Fixed error when using inside dimensions where the height was not correctley calculated.