In a large mixing bowl, combine the ground beef, breadcrumbs, egg, chopped onion, minced garlic, Worcestershire sauce, ketchup, thyme, oregano, salt, and pepper. Mix gently with your hands or a spatula until just combined. Avoid overmixing to keep the meatloaf tender.

Transfer the meat mixture to a clean surface and shape it into a loaf. Place the shaped loaf into the crockpot, ensuring it fits comfortably without touching the sides.

In a small bowl, whisk together the ketchup, brown sugar, apple cider vinegar, and mustard until smooth. This glaze will add a sweet and tangy flavor to the meatloaf.

Brush the glaze generously over the top of the meatloaf. Cover the crockpot with the lid and cook on low for 6 hours or on high for 3 hours, or until the internal temperature reaches 160°F (70°C).

Once cooked, carefully remove the meatloaf from the crockpot using a spatula. Let it rest for about 10 minutes before slicing to allow the juices to redistribute.