Two styles of sanding blocks for use with 5" sanding discs. 

I used self-adhesive foam from the craft store as the bottom pad and PSA discs available from any woodworking shop. You can also use adhesive hook-and-look pads for use with hook-and-loop sanding discs. 

I also used the fuzzy skin setting in Cura for texture the outside to increase grip, but I'm sure it would work without it.