Take the frozen meatballs out of freezer the night before you want to use them and place them in the refrigerator. To heat the marinara sauce
, place in a bain-marie on very low simmer, making sure to mix often. To make the bain-marie, just fill a pan that will be able to hold your bowl with the sauce with water halfway up the sides. Simmer until your meatballs are hot on the inside, about 20 minutes. Use the same method if you are warming the sauce without meatballs.