Video:  

This is a 3D printable version of 

I added a pocket to one of the pieces so you can hide things inside

The files are named with their size and the clearance between pieces. The "pocket" files are the ones with a hole to hide stuff in, the other files are solid.

For more customization, the original PARAMETRIC CAD model is on  , so feel free to fork it, change the size, the clearance, and add whatever cute embossings you want