Heat a large cast iron pan or griddle over high heat and let this heat up for 1-2 minutes. Add the teaspoon of oil to the pan and let this heat up for 1 minute. Add the steak, frying on each side for 3 minutes, or to desired doneness. 3 minutes per side will yield approximately medium rare doneness for an average cut of flank steak. Carne asada and skit steak will need less time. If the pan starts to smoke too much, reduce the heat to medium-high. You want the steak browned, not burned. Remove from the pan and let sit, tented with foil, for 5 minutes.