Pre-heat the oven to 400˚F. Bring a pot of salted water to a boil and cook about half way. Drain and set aside.
In a medium bowl mix together ricotta cheese, spinach, artichoke hearts, 1-1/2 cups mozzarella cheese, parmesan cheese, egg, garlic, salt, pepper and chili flakes.
Pour about half of the marinara into the bottom of a 9x13 baking dish.
Spoon cheese mixture into each shell equally and lay into the baking dish. Top with remaining marinara sauce and mozzarella cheese, and bake for 20 minutes.