Searing 

Take the flank steak out of the refrigerator 30 minutes to one hour prior to cooking to bring it toroom temperature. In a very hot cast iron skillet, heat canola oil. Sear on one side for 3-6 minutes, depending on thickness and your preferred doneness. Flip over and sear on the other side for another 3-4 minutes. 

Grilling 

Take the flank steak out of the refrigerator 30 minutes to one hour prior to cooking to bring it toroom temperature. Make sure you clean your grill grates well before you begin. Char build up on the grates will impact the flavor of your steak. Get the grates as hot as possible. Sear on one side for 3-6 minutes, depending on thickness and your preferred doneness. Flip over and sear on the other side for another 3-4 minutes. 

Resting and Serving 

Cook the steak to an internal temperature of at least 125ºF -135ºF depending on your preferred doneness, because it will continue to rise in temperature after leaving the oven. After you cook your steak to your desired temperature, make sure to let it rest 5-10 minutes before you carve. This allows the juices to redistribute.