I went out today to test a paintbox I fashioned out of a cigar box. The weather was overcast and raining, not ideal painting conditions. But this was one of the reasons I wanted a small portable box. I wanted something small enough to use in the truck or when I take longer hikes thru rough terrain.
My paints, brushes, pallette knive fit inside. I taped a 5x7 panel to the lid (tape on the back of the panel to the lid). I glued two strips of wood inside the box, top and bottom. I cut a piece of masonite for my pallette that sits on top of the strips of wood when painting and also acts as a lid to keep everything inside. To keep the lid in a upright position when painting I put a screw in the lid and side of the box and used hanging wire to hold the lid tight.
The box worked great, I painted this with the box on my lap in the truck. This will work equally as well in the woods sitting on a rock or log.