The SIMPLEST Low Carb Meatball Casserole Start with a bag of frozen meatballs. Check the package, this one has 3 grams of carbs for 6 meatballs. Place in a casserole dish then cover with chopped spinach and top with low carb marinara sauce and spread out. Lastly, top with shredded mozzarella cheese. Then bake this at 350 degrees for 30 – 35 minutes. I served mine on top of cottage cheese and for the non low carb family, they got theirs over noodles. Simple and delicious. Ingredients: 16 oz froze