I got an inexpensive plastic corrugated board from the hardware store and flipped it over to use the back. I got plastic (not cardboard) so that it's WATERPROOF.
The water cup MUST have a lip on it. (dollar store)
Position the cup where you want it and trace it with a sharpie. Trace the BOTTOM of it! Make sure the hole is smaller than the lip.
I decided to cut a shape for the thumb hole on my palette too. (This is optional if you don't use a thumb hole.) A bulldog clip can hold your palette to the board.
Ready to cut...
Cut with an X-acto knife. Ready to assemble...I pushed the cup in only half way. Then added a bull dog clip, just for a little extra reinforcement. : )
Don't forget the lid!
The space between the cup and palette holds an extra brush.
All done. And my thumb fits into the hole perfectly so I can hold the board with one hand. This will work perfectly while I stand, or sit, when painting in life classes, urban sketching or plein-air painting. It's nice and light. Can't wait to try it out!
I've left an extra bit on the right so that I can clip a cloth/paper towel there. Happy Painting Everyone!