I have read that a perfect Zentangle Tile holder is the old 3.5 floppy disk storage cases. Online they cost a lot because they people are tagging them “vintage”. You can find them occasionally in used goods stores. I was getting ready to buy one, but I first went over to paperboard boxes area and found a perfect Zentangle Tile storage box. It is a used Martha Stewart Crafts Ribbon Storage Box. The inner dimensions are just over 3.5″ x 3.5″ and the official tiles fit like they were made for it! Oh happy day! I also use Zentangle Apprentice Tiles and about 50 of them also fit sideways in the box with the lid closed.