The Gridfinity system by https://thangs.com/designer/ZackFreedman is pretty cool and all, but one thing I haven't found (on like the first page of stuff because I have the attention span of a goldfish) is a base system for it that is modular. I've seen parametric bases, but not fully modular ones.

I had created a version already, but I had intentionally avoided overhangs with that which made the connectors a bit tough to print. Now the challenge in this one is just a little bit of overhang. Personally I like this one better. I found my first attempt at the connector a bit loose with my normal tolerances so I made one with tighter tolerances. Use whichever one gives you a nice fit.

I removed most of the outer corner radius on these to make them a little more aesthetically pleasing (to me) when they are put together. There is an indentation to place a small magnet in (15mm dia, 2mm tall) if you want to have magnets to help hold your stuff in place.

The main one I am going to be using is the "low profile" version which is technically only Gridfinity compatible because it trims a couple mm off the top for a quicker print with a tiny amount less material used. I also included the model with the full indentation size if you want to use that.