In a small bowl, combine the brown sugar, granulated sugar, smoked paprika, garlic powder, kosher salt, and black pepper. Stir with a fork until no clumps remain. Set aside.
Remove the frozen pork belly from its packaging. Pat the surface dry with paper towels to remove any frost or ice crystals.
Rub the entire surface of the frozen pork belly with the oil. The oil helps the spice rub adhere to the frozen meat.
Press the spice rub firmly into all sides of the pork belly, coating it generously. Don't be shy — frozen meat takes seasoning less readily than thawed meat.
Preheat the air fryer to 400°F (200°C) for 3 minutes. Lightly spray the basket with cooking spray or brush with oil.
Place the pork belly fat-side or skin-side down in the air fryer basket. Cook at 400°F for 18–20 minutes total, flipping the pork belly every 5 minutes for even browning.
After 12–15 minutes, the pork belly will be soft enough to cut. If desired, remove it briefly, cut into 1-inch cubes, and return to the basket for the final 5 minutes for extra-crispy edges.
Check the internal temperature with an instant-read thermometer. It should reach at least 145°F (63°C) for safe consumption, or 195°F (90°C) for the most tender, melt-in-your-mouth texture.
Remove from the air fryer and let rest on a plate for 3 minutes. Serve immediately with your favorite dipping sauce, over rice, or in bao buns.