Pre-heat the oven at 400 F / 200 C
In a bowl, mix psyllium husk and water and let rest 4-5 minutes until it becomes gelatinous
Add flours, potato starch, baking powder and salt to a large bowl and mix well
Add water and the psyllium gel to the dry ingredients and mix them using a fork, incorporating all the ingredients as much as possible, untile you have a "crumbly" mixture
Move the dough mix to a lightly floured (with white rice flour) worktop and work the dough with your hands for 4-5 minutes, until you can shape it into a smooth, uniform ball of dough
Generously grease the sheet pan with the olive oil
Place the pizza dough on the sheet pan and press it with you hands, spreading it out up to the pan rims
As soon as the pre-heated oven has reached the baking temperature, cover the pizza base with seasoned tomato sauce and all the toppings you love (do not do this before, or the dough will soak the toppings liquids and won't cook properly)
Place the sheet pan pizza on the lowest oven rack for 12-15 minutes, then move it to the middle rack for another 20 minutes, or until the crust is golden (with a spatula carefully lift a corner of the pizza to check that the bottom is nice and golden-brown too)
Enjoy your pizza, adding fresh ingredients like basil or arugula once out of the oven!
Left over pizza is best enjoyed after re-heating it a couple minutes in the microwave.