Pour the orange juice, sugar, vinegar, soy sauce, ginger, garlic, and red chili flakes into a medium saucepan. Place over medium heat and let it warm for about 3 minutes, stirring occasionally. In a small bowl, stir together 1 tablespoon of cornstarch with 2 tablespoons of water to make a slurry. Slowly add this mixture into the saucepan while whisking. Continue to cook for another 5 minutes until the sauce thickens enough to coat the back of a spoon. Once it reaches this point, remove from heat and stir in the fresh orange zest. Set aside.

In a shallow dish, combine the flour, cornstarch, and a generous pinch of salt. Mix well. In another shallow bowl, beat the eggs until smooth. Take each chicken piece and dip it first into the egg mixture, then into the flour mixture. Make sure each piece is fully coated. Set them aside on a plate.

Fill a heavy-bottomed pot with about 2 to 3 inches of oil and place over medium-high heat. Use a thermometer to monitor the oil and wait until it reaches 350 degrees Fahrenheit. Once hot, carefully add a few pieces of chicken at a time, making sure not to overcrowd the pot. Fry each batch for 2 to 3 minutes, turning occasionally, until golden brown and fully cooked inside. Transfer the cooked chicken to a plate lined with paper towels. Repeat until all chicken is fried.

Place the fried chicken into a large mixing bowl. Pour the warm orange sauce over the top and gently toss to coat each piece evenly. If you like, reserve some sauce to drizzle over rice. Serve hot, garnished with sliced green onions and a bit of fresh orange zest for extra flavor and color.