In a large bowl, toss the chicken pieces with cornstarch, salt, and pepper until evenly coated.
Heat olive oil in a large skillet or wok over medium-high heat. Add the chicken and cook, stirring occasionally, until browned and cooked through. This will take about 6-8 minutes. Remove the chicken from the skillet and set aside.
In a separate bowl, whisk together the orange juice, soy sauce, honey, rice vinegar, cornstarch, ginger, garlic, and red pepper flakes (if using).
Pour the orange sauce into the same skillet and bring to a simmer over medium heat. Cook, stirring constantly, until the sauce thickens slightly, about 2-3 minutes.
Add the cooked chicken back to the skillet and toss to coat evenly with the orange sauce.
Serve immediately over rice or noodles. Garnish with orange zest and sesame seeds. Enjoy your Easy Orange Chicken!