
In a saucepan or skillet, combine orange juice, sugar, soy sauce, rice vinegar, cornstarch, ginger, garlic, and red pepper flakes.
Bring it to a boil over medium heat. After 4-5 minutes, the sauce will begin to thicken. Mix it well.
Turn off the heat and add the orange zest. Give it a quick mix and allow the sauce to cool down.
Later, transfer it to an airtight container and use the orange chicken sauce when needed.