Heat olive oil in a large skillet over medium heat.
Season the chicken breasts with Italian seasoning, salt, and black pepper on both sides.
Once the oil is hot, add the chicken breasts to the skillet and cook for 6-7 minutes on each side until golden brown and cooked through (internal temperature should reach 165°F/75°C).
Once the chicken is cooked, layer the tomato slices evenly over each chicken breast.
Place mozzarella slices on top of the tomatoes and cover the skillet with a lid. Let it cook for an additional 2-3 minutes until the cheese melts.
Remove the skillet from heat and add fresh basil leaves on top of each chicken breast.
Drizzle balsamic glaze over the chicken and sprinkle with red pepper flakes, if using.