Dissolve sugar in 150ml of lukewarm water and stir in the dried yeast.
Allow the yeast mixture to sit for 5 minutes until frothy.
Combine rice flour, potato flour, tapioca flour, dried milk, baking powder, xanthan gum, and salt in a mixer.
Whisk sunflower oil and egg together then add to dry ingredients on low speed.
Add yeast mixture and remaining 75ml of water to the bowl.
Mix for 4 minutes using a K-blade until a smooth dough forms.
Divide dough into four 150g portions on a floured surface.
Flatten each portion into a 20cm circle on a parchment-lined tray.
Cover with a towel and let rise in a warm place for 15 minutes.
Preheat the oven to 200°C.
Bake the plain bases for 10 minutes.
Add toppings and bake for another 15 minutes until golden.