1. Preheat the oven to 325°. Place the garlic on a sheet of foil; drizzle with 1 teaspoon olive oil and 1 tablespoon water. Seal and bake until soft, about 30 minutes; let cool slightly. Squeeze the garlic cloves from their skins into a small bowl; add 2 teaspoons olive oil and mash into a paste.
2. Meanwhile, grease a baking sheet with the remaining 1 teaspoon olive oil; dust with the cornmeal. Stretch the pizza dough into a large rectangle and transfer to the prepared baking sheet. Let the dough rest for 10 minutes; stretch again to almost fill the pan.
3. Position a rack in the lower third of the oven and preheat to 425°. In a medium skillet, cook the bacon over medium heat, stirring often, for 5 minutes; drain and transfer to a plate. Add the spinach to the skillet and cook over low heat until warmed through; season with salt and pepper.
4. Brush the pizza dough with the garlic paste. Top with the spinach and dollops of ricotta. Sprinkle with the bacon and mozzarella. Bake for 15 minutes, lower the temperature to 400° and bake until the cheese is brown and bubbling, about 10 minutes.