I designed a deckbox for Magic: the Gathering, EDH/Commander. I've seen similar online, but never with free STLs. Took quite a few iterations. I made everything from scratch in Tinkercad except the symbols. Those I pulled from the links below. I have a blank lid and all 10 guild lids which use the inlay method (so printed with a single extruder). If you're unsure what that is, I'll link that below as well.

Per request, there is also a Core with dice area and a lid for that. I have not printed them, but they should work fine.

Front has a slot for a top-loader for your commander. I used some self adhesive felt on the inside front and back to keep from scratching the sleeves. There's room for felt on the sides, but the corners of sleeves catch. If you used something smooth instead of felt you could pad the whole thing.

Entire print is supportless. Printed on an Ender 5 Pro with Sunlu PLA.

Lid is attached with 1/8 inch cube N40 magnets. You can get them from hobby stores, or I've provided both Home Depot and KJ Magnetics links below. They're nearly press-fit, but a drop of super glue underneath to secure them is probably needed.

Guild Symbols - https://www.thingiverse.com/thing:2791210 Planeswalker Symbol - https://www.thingiverse.com/thing:1670628 Inlay- https://www.youtube.com/watch?v=0Sla-vIsvh4 Magnets - https://www.homedepot.com/p/Magcraft-Rare-Earth-1-8-in-Cube-Magnet-100-Pack-NSN0570/204721266 https://www.kjmagnetics.com/proddetail.asp?prod=B222G-N52