To make it, you need a piece of corrugated plastic (I got it from my art supply store, but Stephanie says you can get it from hardware stores as well); a prescription pill bottle, and a binder clip to hold your palette. Just cut two circles in a piece of corrugated plastic cut to size (mine is 8" x 7.75"). Add tape to protect your thumb against the cut edges of the plastic. Put down some scrap watercolor paper to test your colors, clip on your palette, add water to your pill bottle, and hold some paper towel or tissue in your hand underneath the palette and you're ready to go!
I can't wait to try this out in the field!
Do you have your own portable palette solution? I'd love to hear about it!
UPDATE: I added a couple of holes to the palette to hold some paint brushes.