Place the mozzarella sticks in the freezer for at least 30 minutes to prevent them from melting too quickly during the air-frying process.
In a small shallow bowl, whisk the egg whites until they are slightly frothy.
In a second shallow bowl, whisk together the oat flour, grated parmesan, garlic powder, dried oregano, sea salt, and black pepper until well combined.
Dip each frozen mozzarella stick into the egg whites, then roll it in the flour mixture, then dip it back into the egg whites and once more into the flour for a thick, double coating.
Arrange the coated sticks in a single layer in the air fryer basket, ensuring they are not touching, and spray lightly with a mist of avocado oil.
Air fry at 400°F for 5 to 7 minutes until the crust is golden brown and the cheese is just beginning to bulge but not burst.
While the sticks cook, warm the marinara sauce in a small saucepan over low heat and serve immediately as a dipping sauce.