Meatball Sub Bake

Preheat the oven to its highest temperature setting, which is 425 degrees Fahrenheit or 220 degrees Celsius.

Place the garlic bread on a baking sheet with its spread side facing upwards and bake it in the preheated oven until warm, golden brown, and crispy on top. This should take around 10 to 12 minutes, at which point you can set it aside to cool down.

To prepare the second part of your dish, reduce the oven temperature to its next lower setting, which is 350 degrees Fahrenheit or 175 degrees Celsius.

In a large cooking vessel, bring the spaghetti sauce to a rolling boil. Once boiling, add in the frozen meatballs and continue to cook until they are heated through. This process should take around 20 minutes, at which time the meatballs will be fully cooked.

Now it's time to assemble your casserole. Tear the garlic bread into small, manageable pieces and spread them evenly across the bottom of a 9x13-inch baking dish. Pour the spaghetti sauce and meatballs over the garlic bread, making sure to coat every piece of bread with the savory sauce and distribute the meatballs evenly throughout.

Add a layer of melted mozzarella cheese on top of the casserole, followed by a layer of grated Parmesan cheese. This will provide a rich and creamy texture to your dish.

Finally, place the casserole in the oven and bake it until the cheese has melted and is golden brown, taking around 20 to 25 minutes.