Place flank steak in a large zip top bag or shallow container. Pour sauce over flank steak. Turn the steak until it has been completely covered in the marinade. Marinate in the refrigerator for at least two hours but up to 24 hours.
When ready to grill, remove from fridge and discard excess marinade.
Grill steak over high heat, flip every 45 seconds for 7-8 minutes or until it reaches desired internal temperature.
The longer you marinate the steak, the more flavor! I recommend marinating it overnight, but if you don't have enough time, be sure to marinate for at least an hour or two.