Preheat the oven to 400 degrees.
Spray a 12-inch round pizza pan with vegetable oil spray, and then sprinkle it with corn meal. Fill a small bowl with some cool water.
In a large mixing bowl, whisk together the sorghum and millet flours, the potato and tapioca starches, salt, and guar or xanthan gum. Combine the water, yeast, oil, and sugar and mix for 1 minute. Pour this wet mixture into the bowl of dry ingredients and mix well. This should yield a sticky dough.
Drop the dough onto the center of the pizza pan. Dip your fingertips into the water bowl and gently press the dough out to the edges of the pan. You will need to dip your fingers repeatedly to prevent sticking.
Bake the bare dough for 10 minutes. After 10 minutes, use a fork to prick the top of the crust several times, then bake it for an additional 5 minutes. Remove the dough from the oven, load it up with your favorite toppings, and then bake the topped dough for 10-15 minutes, until the crust turns golden brown.