Salt steaks generously on all sides. Place at room temperature for 45 minutes before cooking.
Preheat an area of the grill to high heat and another area to low heat. Brush grates with olive oil.
Season steaks with black pepper and, if desired, a dash of steak seasoning.
Place flat iron steaks on the hot area of the grill for 3-4 minutes to sear. Flip to the other side with tongs and sear for 2-3 minutes.
Move steaks to the low-heat area of the grill to finish cooking to your level of doneness. For medium-rare, remove steaks when they reach 125 degrees; adjust accordingly for other doneness levels.
Rest steaks for 5-10 minutes on a plate tented with foil before serving.