These Crockpot Salisbury Steak Meatballs are an easy, comforting meal made by slow cooking frozen meatballs in a rich, savory gravy made from beef broth, brown gravy mix, onion soup mix, ketchup, and Worcestershire sauce. Thickened with a cornstarch slurry, the dish is perfect served over mashed potatoes or egg noodles, making a hearty dinner for the whole family with minimal prep.