Preheat the oven to 350°F (175°C).
In a large bowl, combine ground beef, breadcrumbs, onion, garlic, eggs, ketchup, Worcestershire sauce, oregano, salt, and pepper.
If using, sprinkle in the gluten-free flour gradually, mixing until just combined.
Shape the meat mixture into a loaf form and place it in a greased baking dish or lined baking sheet.
Spread additional ketchup on top for a flavorful glaze.
Bake for 1 hour or until the internal temperature reaches 160°F (70°C).
Let the meatloaf rest for 10-15 minutes before slicing.
Garnish with chopped parsley before serving.