Holds three tiles and has a compartment for balls. I called it the Battle Bracer because I intend to put it on my arm, Yu-Gi-Oh Duel Disk-style, but it could work fine as a Battle Board, too.

The wrist mount that I used is just the Wrist Changer but I filled in the part that accessories attach to and just hot glued it to the board. https://thangs.com/designer/models/3d-model/33575?part=7bff7c8d-554d-4a66-8bf3-405459f1e82b