Make one
Cut them at the Sawmill table. They come in packs and take one cell of your pack each. The small drawing board is a smaller sign. The big one needs the sawmill's power feed.
Hang it
Hang it on a wall and take it down by hand again. It snaps to the grid like a bench.
Draw and rub out
Make a charcoal pencil at the alchemist's table, then write or draw on the board. Rub out with your bare hand or the pencil's eraser end. The board keeps its drawing.
CarefulEvery blow wears a board, and it breaks like anything else.