You can buy these boards, called “watercolor boards”, at Jerry’s or ASW online, but it was too late for me to order one. You can buy materials to make them locally and probably much cheaper. I made a trip to our local Home Depot and found just what I needed.
The material will probably be located by the lumber and trim. It’s a corrugated white plastic called Plaskolite – you can hopefully read that here.
As you can see, I rounded the corners so I wouldn’t poke anyone! I just used an Xacto knife and drew the curve by running a pencil around the edge of a cup.
Then I cut out a “handle” and wrapped it with art tape. I’m sure you could do something much neater than I did, but, hey, it works! And, “if it works, it’s perfect” – that’s my motto!
Let me know if you make any of these and how they work for you!