Creating Creamy Southern Spaghetti Bake is straightforward if you follow these simple steps:

1. Preheat your oven to 350°F (175°C).
2. Cook the Spaghetti: In a large pot, boil salted water and cook spaghetti according to package instructions. Drain and set aside.
3. Mix the Cheese Filling: In a large bowl, combine ricotta cheese, sour cream, 1 cup of mozzarella cheese, ½ cup of Parmesan cheese, garlic, Italian seasoning, red pepper flakes, and salt and pepper. Mix until well combined.
4. Prepare the Meat: If you haven’t already, cook the ground beef or sausage in a skillet until browned. Drain excess fat.
5. Combine Ingredients: In a large mixing bowl, combine the cooked spaghetti, meat mixture, and marinara sauce. Stir well to coat the spaghetti evenly.
6. Layer the Dish: In a greased 9×13-inch baking dish, spread half of the spaghetti mixture. Then, spread the cheese filling evenly over it.
7. Add Remaining Spaghetti: Top the cheese layer with the remaining spaghetti mixture.
8. Sprinkle with Cheese: Finally, sprinkle the remaining mozzarella and Parmesan cheese on top.
9. Bake: Cover the dish with foil and bake in the preheated oven for 20 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
10. Cool Before Serving: Remove from the oven and let it cool for about 10 minutes before cutting into squares.

These steps will ensure a delicious and satisfying Creamy Southern Spaghetti Bake that your family and friends will love.