This is my first design, so be gentle. My major project right now is I’m turning this poker table into a D&D table. One thing I knew I wanted was cup holders for everyone. I was shocked that I couldn’t find a good Gridfinity Cup Holder on any of the major STL sites (found some, but wasn’t impressed, and really wanted to cram some D&D features in this so let me break it down:

a 3x3x6 Gridfinity Bin
2 sizes of cup holder using a similar design as what a lot of cars have in them. The inner ring holds cans and the outter ring allows for a standard coffee mug. I drink out of 32oz deli containers a lot and they fit perfect.
Pen Slots, will hold most pens and highlighters. A little big for pencils but they fit and rattle a little.
Dice tray. I tried a lot of designs for this before settling on a deep try. I really wanted a slot for each but they were just too close together to fit 7. Still, I like the tray because it makes it functional for more than just D&D now, you can just use it as a cup holder with extra storage anywhere you need one.
Notepad/Sticky Notes/ Note card slot: this can be used for all kinds of things like spell cards and notes. It was originally based on a standard Sticky Note Pad, but I wanted to fit Field Notes in there, I realized that if I pushed the square all the way out, it could be used for just about anything, plus it looks sick with that angle.
The best for last, a 22 mm miniature slot that doubles as a dice roller! This was challenging to make, but it turned out great and I’m really proud of having something so dynamic in the design.

As far as printing instructions go, I would recommend you use the same settings as you do for any other gridfinity project. Hard to be specific because it depends on how ok you are with "rough" looking gridfinity boxes. Personally I use 10% infill and no more than 3 walls, but they are more functional than aesthetic.

I have also included just the cup holder with no extra holes. Feel free to remix and use this however you see fit, not attribution required...This design is open source and I would love to see others improve upon it.