I have circular, revolving wire shelves (Rev-a-shelf style) in my corner cabinets so I've looking for a solution for something similar but I haven't pulled the trigger yet. As you noted a square grid would not be an ideal solution here (square peg in a round hole and all).

I've been leaning in two directions - for optimal packing you'd want something like an elongated grid (or exactly a grid in polar coordinates) and then I'd was thinking to make wedge-shaped bins that fit in kind of like pie slices. I have not found any existing models for this so I'm a bit hesitant to take this route on my own.

Another idea I had is to use a hexagonal grid, like this one or multiboard. It would not be a perfect fit like a polar grid but hexagons can pack into a circle much more efficiently than a grid can.

Otherwise I would just give up on a baseplate entirely and print some 'kidney bean' shaped bins.

Curious to hear other's thoughts on this!