Slice the flank steak into small thin pieces against the grain. In a large ziploc bag add the starch and the beef to it. Close the ziploc bag and shake really well until each pieces is coated with cornstarch.
In a non stick skillet heat the oil. When the oil is hot, add beef and cook until browned. It will take 2 or 3 batches because you don't want the steak pieces to stick to each other. Also if you need more oil after the batch feel free to add more. Remove beef from skillet to a plate and empty the oil from the skillet.
Add the bell pepper to the skillet and saute it for a couple minutes just until it gets soft. Remove the pepper from the skillet to a plate and set aside.
In that same skillet add sauce ingredients, the sesame oil, soy sauce, brown sugar, garlic, chicken broth and red pepper flakes. Stir and cook over medium heat until sauce thickens a bit and reduces by about a quarter. It took me about 10 minutes until the sauce thickened and reduced. You don't want to reduce it too much because you need more sauce for the noodles.
In the meantime cook the ramen noodles according to package instructions.
Return the beef and bell pepper to the skillet and toss in the sauce. Add the cooked ramen noodles to the skillet and toss everything together. Top with green onions and serve.