Designed in Fusion 360...quite pleased indeed :)
You will need to flip the design in your slicer so you can see the recessed bolt holes and the washer/spacers are level on the bed :)
Uses 22mm skateboard/fidget spinner bearings, 8mm nuts and bolts (found in the garage).
I did revise the file for slightly larger holes and washers as they were a bit tight so these should be spot on. :) PLA 190c bed 60c...I did start bed at 70 for the first layer but think it was a bit warm.
PS preview shows the bottom! odd but the other side shows the recessed holes for the nuts and bolts.