Crumple foil into balls for a trivet and oil the slow cooker lightly.
Stir breadcrumbs and milk in a large bowl; let sit 5 minutes.
Whisk in eggs, ketchup, Worcestershire, onion, garlic, parsley, salt, pepper, and paprika.
Add ground beef and mix gently with your hands until just combined.
Shape into a tight loaf, about 8 inches long, without overworking.
Set the foil trivet in the cooker and place the loaf on top.
Whisk ketchup, brown sugar, mustard, and vinegar to make the glaze.
Brush the loaf with half the glaze.
Cook covered on Low 5 hours or High 3–4 hours, to 160°F internal.
Brush with remaining glaze and cover 15 minutes to set.
Lift out, rest 10 minutes, then slice and serve.
Notes
Variation: Swap half the beef for ground turkey for a lighter loaf, or add 1/2 cup finely diced mushrooms for moisture. Tip: For a sticky, caramelized finish, broil slices on a sheet pan for 2–3 minutes before serving. Storage: Refrigerate slices in an airtight container up to 4 days, or freeze up to 2 months.This recipe is an original creation inspired by classic Easy Slow Cooker Meatloaf flavors. All ingredient ratios and instructions are independently developed.