Slice your flank steak into thin strips. Be sure to cut against the grain. Place the beef in a bag with the arrowroot powder and soy sauce. Mix and let it sit for 30 minutes
In a small mixing bowl, add your lo mein sauce ingredients. Stir well and set aside.
Prepare your lo mein noodles according to the package. Set them aside.
Preferably using a wok over medium high heat, add 1 tablespoon of sesame oil. Let it smoke a little and add your beef. Be sure to not overcrowd so every piece of meat is touching the pan/wok.
Let the meat brown for about 2 minute per side. Remove from wok and set aside.
Add another tbsp of sesame oil and add your garlic, carrots and peppers. Stir fry for 2-3 minutes being sure to not let your garlic burn.
Add your prepared lo mein noodles and sauce. Stir well.
Add your beef back in along with your snow peas. Stir fry together for a few minutes until your noodles are heated through to a golden color.
You can always add more sauce as you wish.