Line a slow cooker with a heavy duty aluminum foil sling. Spray the foil lightly with nonstick cooking spray.
Gently combine all ingredients (except ketchup) in a large bowl. Just be careful not to over-mix, or the meat will be tough. I like to use my hands for this!
Shape beef mixture into a loaf and place in the foil sling.
Spread a thin layer of ketchup over the top of the meatloaf.
Cover and cook on LOW for 4-6 hours or on HIGH for 2-3 hours, or until a meat thermometer inserted in the center of the meatloaf reads 160°F.
Remove meatloaf from slow cooker. If you like a more sticky, caramelized glaze on top, add a little bit more ketchup to the top of the meatloaf, place it on a rimmed baking sheet, and place it under the broiler until it reaches the desired consistency. Keep a close eye on it because it can burn quickly! Transfer to a cutting board, slice and serve.