3 cans crushed tomatoes (28 oz) - No salt added variety
2 cans diced tomatoes (14.5 oz)
5 garlic cloves (or 3 tbsp of minced garlic)
1 large onion, chopped
2 tbsp dried oregano
2 tbsp dried basil
1 tsp red pepper flakes
1 tsp salt
1 tsp pepper
Mix all of the ingredients into a slow cooker.
Cook on low for 8 hours. Let cool completely before freezing.