I thought I might try some geometric shapes as filament samples but liked the softer corners. 

These print quick and the 12x3mm button magnet press fits in the bottom, The 2mm recess for the magnet leaves a nice gap the makes them easier to move etc 

Its a hexagon with a recess in the bottom feel free to remix and reuse i don't own the  rights ti a shape just let me know what you do with it