Here are a couple recipes for making paste. I've been interested in creating natural, biodegradable art supplies. Please note that I haven't tried these recipes myself.
Rice (starchy, not Basmati, and not rinsed)
Cook rice with twice the water you'd normally use. Overcook until gooey over low heat.
This is how Sinian made paste with her grandmother as a child in China.
Boil together. The thicker, the better.
May get moldy quickly.
Lesson plan by Heather Taylor, firstname.lastname@example.org. You are welcome to share all materials with credit to her.