Prepare the toppings: In a small skillet, heat the olive oil over medium heat. Add the spinach and cook for 2 minutes until wilted but still bright green. Add 1 pinch salt and remove from the heat.
Thinly slice the red onion. Slice the olives in half. If the sundried tomatoes are large, you can chop them smaller too.
Bake the pizza: When the oven is ready, dust a pizza peel with cornmeal or semolina flour. (If you don’t have a pizza peel, you can use a rimless baking sheet or the back of a rimmed baking sheet. But a pizza peel is well worth the investment!) Stretch the dough into a circle; see How to Stretch Pizza Dough for instructions. Then gently place the dough onto the pizza peel.
Spread the pizza sauce over the dough using the back of a spoon to create a thin layer. Add the shredded mozzarella cheese. Top with the cooked spinach, red onion, olives, sundried tomatoes. and feta cheese.
Use the pizza peel to carefully transfer the pizza onto the preheated pizza stone. Bake the pizza until the cheese and crust are nicely browned, about 5 to 7 minutes in the oven (or 1 minute in a pizza oven).
Allow the pizza to cool for a minute or two before adding the basil on top (whole leaves, lightly torn, or thinly sliced). Slice into pieces and serve immediately.