Crock Pot Meatball Sub sandwiches have only 4 ingredients. You can have dinner on the table in under 4 hours if you are in a hurry or it can cook for the standard 8 hours in a crock pot on low.
Pour ⅓ of the meat sauce into the bottom of the crock pot.
Pour the entire bag of frozen meatballs into the crock pot.
Pour the remaining sauce over the frozen meatballs, cover and cook for about 3 hours on high or until the meatballs are heated through.
20 minutes before serving slice the block of mozzarella cheese and lay the slices over the top of the cooked meatballs . Recover and heat until the mozzarella cheese has melted.
Serve the cheese covered meatballs on your favorite sub rolls.