After finding several gridfinity models on Printables and elsewhere that I really liked, but wished they had magnet holes, I made this quick parametric design in Fusion360 that would let me output an STL that I could import as negative space in PrusaSlicer. You can set hole width, depth, and grid layout in parameters. Hopefully it saves someone else a bit of time.

I will note that after making this all configurable, I realized I could just keep a large one around and use that for most things I was printing.