Similar to the Skirt Steak, these instructions assume the Flat Iron is a little thicker.
Preheat grill to 450-500°F.
Grill about 5-6 minutes per side on a hot grill until 135°F for medium rare.
Allow the steak to rest for 5-10 minutes after grilling before slicing against the grain.
See also Grilled Skirt Steak and Grilled Flank Steak