Add all of the ingredients for the basil pesto into a food processor and process until they come together. Add some water if the pesto seems too dry and isn't mixing smoothly.
To make the cauliflower base:
Preheat your oven to 375 F (190°C).
(If you have readymade cauliflower rice, you can skip this step.) To make cauliflower rice from scratch, take the head of a large cauliflower and cut into smaller florets. Grate these florets using a box grater with medium-sized holes. You can also use a grater attachment on your food processor to make cauliflower rice instead.
Bring a large pot of water to the boil and add the riced cauliflower. Mix and cook for 5 minutes until the rice is soft.
Drain the cauliflower rice with a fine mesh strainer or a kitchen towel. Once most of the water has drained, set the rice aside to cool for 5 minutes.
While the cauliflower rice is cooling, mix the flaxseed meal and water and form it into a ball. Set aside.
Wrap the cooled cauliflower rice in the dish towel and ring out as much water as you can. Put the cauliflower rice in a large mixing bowl.
Add the prepared flaxseed ball, almond flour, oregano, onion powder, sea salt, and chopped basil leaves to the mixing bowl. Combine the ingredients thoroughly using your hands.
Taste the mixture and adjust the saltiness and flavor as needed. You can add more onion powder or basil leaves for more intense flavor.
Spread the dough on a baking sheet dusted with gluten-free flour and shape into a circle. It should be roughly 1/2 inch (1.5 cm) thick with slightly thicker edges.
Bake the crust for 30 minutes and remove from the oven.
Add a thin layer of tomato sauce and your chosen toppings to the base. Bake for a further 10-15 minutes until the edges are golden brown and the base is cooked through.
TIP: Don't use too much tomato sauce or the pizza will get soggy!
Spread some of the freshly prepared basil pesto onto the pizza and serve hot.