Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5218578.
I wanted a horizontal organizer for sleeved Dominion cards, but couldn't find anything quite like what I wanted. I really love the Broken Token insert but since I have a 3d printer I wanted something I could print myself. I quickly mocked this up on Tinkercad and it worked great! It measures 288mm x 98mm x 65mm high. Should be easy to modify to fit any card heavy game.
This is a big file, and the only way I could get it to fit on my printer was to rotate it 45* and it just barely fit. One of the pictures shows this in Cura. Definitely print with a brim. The dividers were a VERY snug fit, and I like them that way so nothing moves around. I only printed 3, but print as many as you want.
This will fit two columns of sleeved cards, but won't quite fit three as you can see in one of the pictures. I took a picture before I sleeved the cards and the Dominion Base game plus the Prosperity expansion fit in one column. After sleeving it takes up one and a half.
Update 2/8/22: I designed and printed a middle piece so the box can stack vertically and the other pieces don't slide around. (In green in the first photo) I made it really thick to hold the weight of the cards whatever direction the box is placed. 20% infill. The two side slots fit sleeved cards as shown in the photo. In the middle I have a prototype of this box: https://www.thingiverse.com/thing:5190061 that I use to hold random coins/tokens. If you do print it, it needs to be scaled down slightly to fit. Scale to 90% in X and Y but Z can stay the same.