Cook the bacon: Pan-fry or bake bacon until crisp.
Drain and crumble. Reserve 1 tablespoon bacon fat if you plan to pan-sear.
Prep the oven or air fryer: Preheat oven to 400°F (205°C). Line a sheet pan with parchment and lightly oil it.
For air fryer, preheat to 375°F (190°C) and lightly oil the basket.
Mix the wet ingredients: In a large bowl, whisk the egg, ketchup, mustard, Worcestershire, and pickle relish until smooth.
Add aromatics and seasonings: Stir in minced onion, garlic, smoked paprika, onion powder, parsley, 1 teaspoon salt, and 1/2 teaspoon black pepper.
Combine the meat mixture: Add ground beef, crumbled bacon, cheddar, and almond flour. Mix gently with your hands until just combined. Do not overwork.
Form meatballs: Scoop about 2 tablespoons per meatball (a small cookie scoop helps).
Roll gently. You should get 22–24 meatballs.
Oven method: Arrange on the sheet pan with space between each. Bake 14–18 minutes, until browned and the centers reach 160°F (71°C).
Air fryer method: Air fry in batches 10–12 minutes, shaking halfway, until the internal temperature hits 160°F (71°C).
Optional sear: For extra crust, quickly sear baked meatballs in a hot skillet with a little bacon fat for 1–2 minutes.
Rest and serve: Let rest 5 minutes.
Serve with burger sauce or ranch, and add low-carb sides like cucumber slices or lettuce cups.