The box is print in place and will require good tolerances on your machine.

For the foam, I used cheap anechoic foam but any soft foam should work. A roughly 2cm strip glued in to the top edge of each side works well, whilst still allowing the mini to be easily placed and removed.

I added text to the back of the lids on my boxes for easier mini selection.

After printing, you need to get the slider moving. It requires quite a bit of force to get it sliding and a little wax on the runners helps a lot once you have it moving.