Make a rug loom with PVC pipe. Weave around top/bottom and sides of PVC to keep the weaving from pulling in. When done, just take apart the PVC and slip off the rug. What a great idea from Pink In Mind. Maybe with T-Shirt yarn?
Like the idea - use a board to save the walls and maybe not Velcro since it'll get gross and isn't easily cleaned. Magnets or even small hole in cup to hang on a hook? Cars, Trucks and Teething Rings: Kids Toothbrush/Bathroom Fix