3 heaping tbsp. flour - put in a pot & slowly whisk the boiling water into the flour
Boil until translucent, whisking continuously to avoid lumps. Will take approx. 3 minutes to cook.
Allow to cool completely.
Will store for up to 1 week in the fridge.
Put a few tbsp. of the water/flour mixture into paper or plastic cups (ones that won't be used afterwards for food), mix in a bit of acrylic paint, then paint your paper. Add a second colour on top, either while the first colour is still wet or after drying. Try various tools to add texture and "scrape" the 2nd colour off the paper. Ideas for tools: old credit card, old fork, stylus, sponges, stamps, etc.
Choose papers that are strong when wet. They may curl as they dry; once dry put heavy books on top for 24 hours to flatten.
I have not yet tried this with gluten-free flour, but will try this when I am next making the paste. Will report back.