Score the steak with a knife - slice the steak vertically and horizontally 1/8" deep.
Mix all of the rest of the ingredients and pour over flank steak. Make sure that you flip the steak to make sure it is well coated. Place steak in a glass baking dish or put it in a gallon ziplock bag.
Let sit at room temperature for about an hour.
Remove steak from marinade and sprinkle with salt and pepper.
Spray grill with cooking spray and grill meat until medium rare.
Let rest for 10 minutes and slice meat at an angle.