Slice flank steak into small pieces.
Warm the oil in a heavy bottom skillet. Once hot, add the steak and cook over medium-high heat for about 10 minutes or until browned on all sides.
In a small bowl, mix together the coconut aminos, brown sugar, garlic, xantham gum and chili flakes. Add the sauce to the steak, turn the heat down to low and let it simmer until thickened. Stir occasionally.
Once the sauce has reached your desired consistency, remove the skillet from the heat. Mix in the green onion and enjoy!