In a large mixing bowl, place the ground beef, eggs, milk, breadcrumbs, onion, garlic, Parmesan, ketchup, Worcestershire sauce, salt, pepper, thyme, and smoked paprika. Using your hands or a spoon, gently mix the ingredients just until fully incorporated—avoid overmixing to keep the meatloaf tender.

Shape the blended meat mixture into a firm loaf and transfer it to the bottom of your slow cooker. For easier removal after cooking, consider placing parchment paper or creating a sling from aluminum foil underneath the loaf.

Secure the lid and cook on the LOW setting for 6 to 7 hours, or on HIGH for 3 to 4 hours, until the internal temperature registers at 160°F (71°C) using a meat thermometer.

Approximately 30 minutes before the meatloaf is finished cooking, combine ½ cup ketchup, brown sugar, and mustard in a small bowl to form the glaze.

Spread the prepared glaze mixture evenly over the top of the partially cooked meatloaf. Replace the lid and allow it to finish cooking for the remaining time.

Once fully cooked, turn off the slow cooker and let the meatloaf sit undisturbed for about 10 minutes. Carefully lift it out, slice, and serve alongside your choice of sides such as mashed potatoes, steamed vegetables, or a crisp green salad.