I took the "Extra Printable Companion Cube" and made a hidden box out of it. The original EPCCube was rendered without one side, I corrected this by cutting the top off the cube and using it for the base segment.
The primary files are placed for best print quality on my FDM machine using support. I undersized the fit of the insert to allow for some part growth in the FDM process.
The "UV" files are a bonus for any lucky makers with access to a UV cure machine.
These files are currently sized to give 1inch^3 volume inside the box.
I added a couple pictures of these parts used as output quality tests on the UV cure machine (scaled down to 25%)
print top, base, and insert. Super glue the insert into the base.