Combine the lime juice, soy sauce, green onions, ginger and red pepper flakes in a resealable plastic bag.
Lightly score steak in a cross-hatch manner on both sides.
Add the steak to a Ziplock bag and press out all the air and seal. Place the bag in a dish to protect against leakage. Marinate for at least 30 minutes or overnight in the refrigerator.
Heat an outdoor grill, contact grill, or indoor grill pan to medium high. Lightly oil pan or grill grates.
Remove the steak from the marinade and let the excess marinade drip off. Pat dry with a paper towel. Season to taste with salt and pepper. Place the steak on the grill; cover and cook, turning once until the meat has reached the desired doneness, 6-8 minutes (depending on thickness of steak) for medium rare. Let the steak rest for 10 minutes before slicing thin across the grain.