Preheat your oven to 475°F (245°C) for optimal flatbread crispiness. If you have a pizza stone, place it in the oven to heat.
While the oven is heating, prepare your flatbreads on a clean surface. If using homemade flatbread, roll it out to your desired thickness.
Spread 1/2 cup of marinara sauce evenly over each flatbread, leaving a small border around the edges.
Lay the sliced mozzarella cheese evenly over the marinara, ensuring coverage but still allowing some sauce to peek through.
Add the thinly sliced tomatoes atop the cheese. Season lightly with salt and pepper.
Drizzle about 1 tablespoon of olive oil on each flatbread to enhance the flavor and texture.
Carefully transfer the flatbreads onto the hot pizza stone or directly onto a baking sheet lined with parchment paper. Bake for 10-12 minutes, or until the cheese is bubbly and the edges of the flatbread are golden brown.
Once baked, remove the flatbreads from the oven and let them cool for a minute. Top with fresh basil leaves, scatter them evenly, allowing them to wilt slightly from the heat.
If desired, sprinkle red pepper flakes for a touch of heat. Cut the flatbreads into slices and serve immediately.