Place your frozen meatballs in the bottom of a 5-quart or larger crockpot or slow cooker.
Pour the tomato sauce over the meatballs, then add the minced garlic, Italian seasoning, onion powder, and garlic powder.
Season with salt and pepper according to your personal preference, keeping in mind that you can always add more later.
Cover with the lid and set your slow cooker to LOW for 3-5 hours, until the meatballs are completely heated through.
About 30 minutes before serving, gently stir the mixture to ensure the sauce and seasonings are well combined and coating the meatballs.
Once done, taste and adjust seasonings if needed. Garnish with fresh chopped parsley and a generous sprinkle of parmesan cheese if desired.
Notes
Don't overcook - While slow cookers are forgiving, leaving the meatballs too long can dry them out. Aim for the lower end of the time range if your crockpot runs hot.
Double the sauce - If you're planning to serve these with pasta, consider adding an extra can of tomato sauce to ensure there's plenty for coating the noodles.
Avoid lifting the lid - Each time you peek, you add about 15-20 minutes to the cooking time as heat escapes. Trust the process!
Layer flavors - For the best flavor development, place the meatballs in first, then pour the sauce and seasonings on top, allowing them to slowly soak in as they cook.
Brown for depth - If time allows, quickly brown the frozen meatballs in a skillet before adding to the slow cooker for a deeper, more complex flavor.
Even cooking - Try to arrange the meatballs in a single layer if possible, or at least ensure they're evenly distributed for consistent cooking.