Set up the breading station. In a large bowl, add the beaten egg. Then, combine cornstarch, flour, salt, and pepper in a food container with a lid.
Preheat your air fryer to 400ºF (204ºC).
Bread the chicken bites. Place the chicken chunks into the egg bowl and toss by hand until each piece is coated. Next, transfer egg-coated bites to the cornstarch-flour mixture. Cover the container and shake until all chicken bites are evenly breaded.
Air fry the chicken bites at 400ºF (204ºC) for 10 - 12 minutes. Put the breaded chicken in the air fryer in a single layer. Spray with avocado oil. Then, flip them halfway through, and spray more avocado oil when necessary. Air fry until it’s crispy and golden brown. Finally, make sure the internal temperature reaches 165°F (74°C) or higher before serving.
Make the orange sauce. Combine orange juice, sugar, rice vinegar, soy sauce, grated ginger, minced garlic, red pepper flakes, and sesame oil in a saucepan over medium heat. Simmer for 5 - 7 minutes or until the orange sauce slightly thickens.
Thicken the sauce. Mix a 1:1 ratio of cornstarch and cold water in a small bowl to create a slurry. Add it to the simmering orange sauce and stir until it thickens to a glaze-like consistency. Remove from heat.
Coat the chicken with the orange sauce. Toss the air-fried chicken bites in the orange sauce until they're evenly coated.
Serve your air fried orange chicken. Garnish with optional sesame seeds and green onions for added flair. Pair it with steamed rice and enjoy!