Tear off a large strip of aluminum foil and press it into the bottom and up two of the sides of a 6-quart or larger Crock-Pot. Spray lightly with non-stick cooking spray.
In a large bowl, combine the ground beef, minced yellow onion, dried breadcrumbs, whole milk, large eggs, kosher salt, and black pepper. Mix until just combined.
Shape the meat mixture into an oval and place it into the foil-lined Crock-Pot. Top with 1/2 cup of the ketchup glaze, cover, and cook on LOW for 6 hours.