I just dropped this on Printables: A FreeCAD based custom size box generator. I've been using it for all kinds of stuff. Maybe some of you lot will get some use out of it, too.
Plug in your parameters, make a box with filament hinges -- No hardware required. No screws, no nuts, no supports, no glue, no Fusion, no proprietary software, no going cross-eyed looking at OpenSCAD code.
(And yes, the default size in the file will make an M:tG card deck case.)