Take two long sheets of aluminum foil and fold them lengthwise into strips about 2-3 inches wide. Crisscross them in the bottom of your slow cooker insert, letting the excess hang over the sides to create handles.

In a large bowl, combine panko breadcrumbs and milk. Let sit for a minute to soften completely.

Add diced onion, minced garlic, beaten eggs, Worcestershire sauce, Dijon mustard, dried thyme, salt, and pepper to breadcrumb mixture. Mix until well combined.

Place ground beef on top of breadcrumb mixture. Gently mix together until just combined. Do not overmix - this keeps the texture tender.

Transfer meat mixture to center of foil sling in slow cooker. Shape into a rounded loaf roughly the shape of a football for even cooking.

In a small bowl, whisk together ketchup, brown sugar, and apple cider vinegar until sugar dissolves completely.

Spread about two-thirds of glaze evenly over top and sides of raw meatloaf. Reserve the remaining glaze.

Cover and cook on LOW setting for 4-6 hours until internal temperature reaches 160°F. Don't lift lid during cooking - each peek adds 15-20 minutes.

About 30 minutes before end of cooking, spread remaining glaze over meatloaf for a fresh, glossy finish.

Use foil sling to lift meatloaf out of crockpot onto cutting board. Let rest 10-15 minutes before slicing to allow juices to redistribute.