I wanted a box for my son to keep his football trading cards in. There are a couple other designs out there already, but I wanted something different than what I was finding. Or maybe they're just difficult to find. So, I designed my own. I made the box from scratch in Blender, borrowing the hinge and latch design from another box design I got elsewhere. (I legitimately tried to find where I got that box so I could give it some attribution, but I downloaded it a while ago and now I can't find it anywhere.) Gave this box to my son as a gift and he's super happy with it. The design is simple, but solid. Just take care twisting the lid while you have it open.

This box is about 3 7/8 inches (98mm) long x 5 1/2 inches (140mm) wide x 3 7/8 inches (98mm) tall.
It has a center divider to keep two stacks of standard sized trading cards - and by "standard size" I mean 2 1/2 inch (63.5mm) x 3 1/2 inch (88.9mm). It can fit quite a few cards in there.
Assembly is straightforward. Lid goes on, pins go in, one pin goes through the clasp, clips go on pins, done.

I am including an individual STL for each part, plus some groupings, as well as my blend file from Blender. Tweak it if you wish. Maybe you just want it a different size. Go for it!

Due to the numerous small edges, this will take a while to print. I would highly recommend printing this in PETG or some other material that holds up better than PLA. Since this is for trading cards, chances are it's going to travel. PLA just doesn't have the heat resistance. But if it's just for storage in a closet or something like that, then PLA will be fine.
I did mine at 50% infill for solidity, but you could go with 20% and be just fine.
I recommend tree supports. There are some holes that will benefit from supports (make sure to clean the support material out of those holes before trying to cram the pins through).
I recommend printing the hardware with a brim. For the hardware, print them all at once and set your brim settings so the brims touch one another and that will add strength to the whole.
Print slowly and you'll get a fine result. I printed the box and lid in one color and the hardware in another. Looks pretty good.