1. Place a pizza stone in the bottom of the oven and preheat the oven to 500°. Allow at least 45 minutes for the pizza stone to heat thoroughly.
2. Meanwhile, on a lightly floured surface, roll out one piece of the pizza dough to a 13-inch round. Dust a pizza peel with flour and slide the dough onto it. Drizzle with about 2 tablespoons of the olive oil and sprinkle with half of the garlic and rosemary. Season with salt and pepper. Dollop 1/4 cup of the fig jam all over the crust, being sure to leave a 1-inch border of dough all around. Scatter half of the cheese and prosciutto over the dough.
3. Slide the flatbread onto the stone and bake for about 15 minutes, until puffed and golden. Transfer the flatbread to a cutting board and let cool for 10 minutes before slicing. Repeat with the remaining ingredients to make the second flatbread. Garnish with the sliced scallion and serve.