Ziploc freezer bags. They take up less room in the freezer. You can split the sides of the bag with a knife, put the block of frozen sauce in a big bowl, defrost it and heat it in the microwave. I bake my meatballs separately and portion them out. I put parchment paper on the microwave turntable and make a ring of meatballs around the bowl the sauce in is. I defrost everything and then toss the meatballs in the sauce to get everything hot.