Squish to combine, remove excess air, and seal.
Thaw.
Pour the contents of the bag of meatballs into the slow cooker. Cook on low for five to seven hours.
Arrange the cooked meatballs on one side of the bread and sprinkle the mozzarella cheese on top. Place the subs back under the broiler until the cheese is melted, then place the other bread half on top to serve.
For the pasta sauce in this recipe, we use our Red Sauce.