Zest the oranges first, before cutting them, until you have about 1 tablespoon of fine zest. Set the zest aside.
Slice the oranges in half and juice them until you have ¾ cup (180 ml). Strain out any seeds or large pulp.
Mince the 3 cloves of garlic and grate 1 teaspoon of fresh ginger.
Pat the chicken pieces dry with paper towels, which helps the coating stick and crisp.
In a mixing bowl, toss the chicken with 3 tablespoons cornstarch, ½ teaspoon salt, and ¼ teaspoon black pepper until every piece is lightly and evenly dusted.
Drizzle in 1 tablespoon avocado oil and toss again so the coating can brown.
Air fryer method: Arrange the chicken in a single layer with space between the pieces, working in two batches if needed. Cook at 400°F (200°C) for 10 to 12 minutes, shaking the basket halfway, until golden and cooked to an internal temperature of 165°F (74°C).
Oven method: Spread the chicken on a lined sheet pan and bake at 425°F (220°C) for 18 to 20 minutes, flipping once, until crisp and cooked through.
While the chicken cooks, combine the orange juice, orange zest, 3 tablespoons soy sauce, 2 tablespoons honey, 1 tablespoon rice vinegar, minced garlic, grated ginger, 1 teaspoon toasted sesame oil, and ¼ teaspoon red pepper flakes in a small saucepan.
Bring the mixture to a gentle simmer over medium heat and let it cook for 3 to 4 minutes so the garlic and ginger mellow.
Stir the 1 tablespoon cornstarch and 2 tablespoons water together in a small bowl until smooth, with no lumps.
Pour the slurry into the simmering sauce, whisking constantly, and cook for 1 to 2 minutes until it turns glossy and thick enough to coat a spoon.
Add the cooked chicken to the saucepan, or transfer both to a large bowl, and toss until every piece is coated in the orange sauce.
Scatter the sesame seeds and sliced green onions over the top and serve right away over rice or vegetables while the coating is still crisp.