In a bowl, combine the chicken pieces with the cornstarch, salt, and black pepper. Toss to coat the chicken evenly.
In a wok or large skillet, heat the vegetable oil over medium-high heat. Once the oil is hot, add the chicken and cook for 5-7 minutes, or until golden brown and crispy. Remove the chicken from the pan and set aside on a plate.
In the same pan, add the garlic and ginger and sauté for 1-2 minutes, or until fragrant.
In a separate bowl, whisk together the soy sauce, orange juice, honey, rice vinegar, sesame oil, and red pepper flakes. Add this mixture to the pan and bring to a boil. Allow it to simmer for 2-3 minutes, or until the sauce has thickened.
In a small bowl, whisk together the cornstarch and water. Add this mixture to the pan and stir to combine.
Return the chicken to the pan and toss to coat in the sauce. Cook for an additional 2-3 minutes, or until the chicken is heated through and the sauce has thickened even more.
Remove from heat and garnish with sliced green onions, sesame seeds, and orange zest.