Minimal frame that can be used with everything that fits commons toploader (4" x 3")
Toploader fits inside the frame and  your cards remains protected

The frame is divided in two parts (top and bottom), you can join them with 8 round magnets (6 mm x 3 mm)

There is also a stand to place the frame on a shelf and a hole in the back to hang it on the wall.

If you want to keep card alligned inside top loader, see the aligner here

You can find more templates for trading cards here

PLA is perfect

AMS is not required
Bottom part have a change color at layer, if you want a different color for the inside.
If you want same color for all parts you can print all parts in a single plate.