In a wide, flat bowl, combine the flour, xanthan gum, salt, pepper, and red pepper flakes, if using.

Add the chicken to the flour mixture, and stir until chicken is evenly coated. Set it aside.

In a medium sauce, whisk the orange juice, cornstarch and sugar, until the cornstarch is dissolved.

Add the rice vinegar, soy sauce, ginger, and garlic and whisk to combine.

Cook over medium heat, stirring frequently, until thickened.

In a large skillet, heat 2 tablespoons of oil over medium‑high heat.

When oil is hot, but not smoking, add chicken in a single layer and cook for 2‑3 minutes or

until the chicken is golden on the bottom. At this point, it should easily come away from the bottom of the pan.

Flip and cook until the second side is golden, and the chicken is cooked through. It should read at least 165°F on an instant read thermometer.

Repeat as necessary until all the chicken is cooked. If you need to cook your chicken in batches, add more oil with every batch to keep chicken from sticking.

Add the orange sauce to the pan with the chicken, and add back in any pieces of chicken that were cooked earlier.

Add the orange zest to the pan, stir, and let everything simmer until all the chicken is warmed through and the sauce is bubbling, 3 to 5 minutes.