Update: Added some gaps in the edges to facilitate extracting the bottom cards. Sorry about that. All other model design is consistent with the original.
After a few of my own designs for interlocking trays using magnets, I came across Popsicle_peon's design and liked it. After a few weeks of use however I found the fit to be a little tight. I also figured that others would want to use sleeved cards for this and other games and so I set about building the customizer you see here for Popsicle's design.
The customizer includes much to play with in the UI, and the code gives you full flexibility. I've tried to comment it to aid those learning to code and also to give me a few pointers should I need to return to it.
The primary unchangeable features in the UI are that the base and walls are 2mm thick and the gap on each side is 28mm to allow most thumbs to get in there. This leads to a minimum sensible card width or around 35mm, which I think should cater to almost all cards out there. Otherwise you're free to twiddle with card width, height and stack size. In addition, you can tweak the "breathing space" around the cards if you want more or less space. You can also adjust that in the stack size (or Z dimension). I'm sure you'll figure the rest out by fiddling.
If you do customize this, please share your customized result and give it a name that shows which card game (or sleeve size) you've dimensioned it for. I hope to see some of your makes and your table layouts using the system.