The marinade for this steak is unbelievable! I can't stop eating it.
Trim flank steak of any fat, sinew and silver skin.
The amount of marinade you will need depends on the size of your steak. The amounts given are for a steak about 3 pounds. Increase or decrease the marinade ingredient amounts as necessary.
Whisk together equal amounts of garlic powder, onion powder, celery salt, black pepper, and salt.
Combine equal amounts of red wine vinegar, Worcestershire sauce, and olive oil. Add the spices to the liquid. Put this marinade along with the flank steak in a large plastic bag. Refrigerate for at least 4 hours, turning after 2 hours.
Take the marinating steak out of the fridge one hour prior to grilling and let it rest at room temperature.
Grill the steak over very hot coals for exactly 5 minutes. Turn the steak over and grill on the other side for another 5 minutes. Remove to a plate and let rest for 5 minutes. Carve at a 35-45 degree angle. This will greatly tenderize the meat.
You can make extra marinade for use as a delicious sauce, but set some aside before adding the meat. Do not use the meat marinade. Throw out any left over marinade after the steak has soaked in it.