Heat oven to 425°F. Lightly oil a large rimmed baking sheet.
Combine cornstarch, flour, salt, and pepper in a bowl. Toss in chicken to coat evenly.
Drizzle coated chicken with vegetable oil and toss again to lightly moisten the coating.
Spread chicken in a single layer on the sheet. Bake 15 minutes, then flip pieces.
Bake 8–10 minutes more, until golden and cooked through.
Meanwhile, whisk orange juice, zest, soy sauce, rice vinegar, brown sugar, honey, garlic, ginger, red pepper, and sesame oil in a saucepan.
Bring sauce to a simmer over medium heat. Cook 4–6 minutes, stirring, until glossy and slightly thickened.
Transfer hot chicken to a bowl, pour sauce over, and toss to coat. Garnish with green onions and sesame seeds. Serve immediately.