Combine marinade ingredients in bowl and add flank steak. Set aside 15 minutes.
Heat 1 Tbsp vegetable oil in large skillet over MED HIGH heat. Remove excess marinade from steak and cook in a single layer, for 2-3 minutes, stirring to cook both sides. Depending on the size of your pan, you may need to do this in batches. Remove steak to plate.
Heat remaining 1 Tbsp vegetable oil, then add peas, carrots and green onion and cook stirring often, 2-3 minutes.
Whisk together broth, soy sauce, honey/brown sugar, rice vinegar, garlic, sesame oil, fresh ginger, cornstarch, and red pepper flakes. Add steak and sauce to skillet, stirring to combine. Sauce will thicken.