Whisk together the marinade ingredients in a small bowl. Place the flank steak in a large resealable plastic bag and pour the marinade over top. Refrigerate for at least 2 hours, up to overnight.
Prepare your grill for high temp, direct heat grilling. Clean the grates and lightly coat with oil. For a gas grill set your burners to high and allow it to preheat for about 5 minutes. For a charcoal grill spread an even layer of hot coals in the grill and fully open all vents.
Grill the flank steak for about 5-7 minutes per side, using tongs to flip occasionally. Cook until it reaches an internal temperature between 135°F for medium-rare and 145°F for medium.
Remove from the grill and cover loosely with foil, then allow the steak to rest for 5 to 10 minutes before slicing.
To slice, set it on your cutting board with the grain running parallel to you. Beginning at one end, hold your knife at about a 45° angle and make thin slices across the grain.