Meatballs can be cooked ahead and refrigerated or frozen. About 30 minutes before you want to serve them, heat them on a parchment-lined baking tray in a 350ºF oven until warm. No need to defrost, just heat them on a parchment-lined baking tray in a 325ºF oven until warmed through. They should take about 10-12 minutes out of the refrigerator or 20-25 minutes if frozen. Then glaze and serve.