1Preheat the air fryer to 200°C (400°F).
2Cut the chicken breast into cubes of about 4 cm (1.5 inches). Place the cubes in a bowl with the first amount of cornstarch and toss well to coat evenly.
3Shake off excess starch and place the chicken pieces in the air fryer basket. Cook for 7–9 minutes, shaking the basket halfway through, until the internal temperature reaches at least 74°C (165°F).
4Meanwhile, in a small saucepan over medium heat, combine orange juice, brown sugar, rice vinegar, soy sauce, ginger, red pepper flakes, and orange zest.
5Let the mixture simmer gently for 5 minutes, stirring occasionally.
6In a small bowl, mix the second amount of cornstarch with a little water to form a thin paste, then stir it into the orange sauce.
7Cook for another minute, stirring constantly, then remove from heat immediately.
8Remove the cooked chicken from the air fryer and toss with the prepared orange sauce.
9Serve immediately, garnished with sliced green onions and sesame seeds if desired.