Meatball subs are in the regular rotation during football season at our house. They can be made with frozen meatballs and jars of marinara sauce, homemade meatballs with marinara sauce, frozen meatballs and homemade sauce, or homemade meatballs with homemade sauce.
I have made them in all of the combinations above and I am not ashamed. Even if you tell me how great the sandwich was you just ate, I will let you know I used frozen meatballs and which brand of jarred sauce I used, if I did.
The secret to great meatball subs using frozen meatballs is the cooking method. Slow, slow, slow. You can cook them on a stovetop, in a crockpot, or in a low temperature oven. You just need enough sauce to cover the meatballs and a little water. If I am using a jarred sauce I add about a quarter cup of water to each jar, this normally takes 2 jars when I cook for a party, replace the lid and shake the water in the jar to get out the last of the sauce and pour it in.