Place the frozen meatballs in your slow cooker, ensuring they are evenly spread out for even cooking.
In a separate bowl, whisk together the beef broth, brown gravy mix, onion soup mix, ketchup, and Worcestershire sauce until well combined and smooth.
Carefully pour the gravy mixture over the meatballs in the slow cooker and stir gently to ensure all meatballs are coated.
Cover your slow cooker and set it on low for 4-6 hours until the meatballs are heated through and tender.
About 30 minutes before serving, combine cornstarch and cold water in a small bowl until smooth, then add it to the slow cooker and stir well.
Once thickened, serve these flavorful Salisbury steak meatballs over mashed potatoes, rice, or egg noodles.