Make Sheet-Pan Pizza Dough; transfer to the oiled pan as directed in step 3, then shape into an oval and sprinkle with 2 tablespoons sesame seeds, patting to adhere. Flip the dough, cover and let rise as directed, then stretch. During the final rise, put a pizza stone or inverted baking sheet in the lower third of the oven and preheat to 500˚ for 1 hour.
Meanwhile, make the spinach: Heat 2 tablespoons olive oil in a large nonstick skillet over medium-high heat. Add the spinach and cook, tossing with tongs, until wilted, 3 to 4 minutes. Stir in the remaining 2 tablespoons olive oil, the garlic, 1/2 teaspoon salt and a few grinds of pepper and cook, stirring occasionally, until the water evaporates and the garlic is just golden, about 3 minutes. Remove the spinach to a cutting board and chop.
Make the ricotta mixture: Combine the ricotta, pecorino, oregano and a few grinds of pepper in a small bowl.
Sprinkle the remaining 1 tablespoon sesame seeds around the edge of the dough to create a 1/4-inch border, pressing to adhere. Sprinkle the mozzarella over the dough up to the sesame border. Top with the spinach, then top with spoonfuls (about 2 tablespoons each) of the ricotta mixture.
Put the baking sheet directly on the hot stone and bake until the crust is browned around the edges and the cheese is golden, 15 to 20 minutes. Let cool slightly.
Loosen the edges of the pizza with an offset spatula, then loosen the bottom. Slide the pizza onto a cutting board; cut into squares.