For a total of 12 oz of steak, I used half a cup of low sodium soy sauce, the juice of half a lemon, 1 tbsp of toasted sesame oil, 3 large cloves of garlic, sliced.
Marinate for 4-8 hours. Place steak and marinade in a ziplock bag so that marinade covers the meat evenly.
Grilling the flat iron steaks
I add a pinch of kosher salt when I am grilling the meat, just a pinch will do.
Preheat a cast iron skillet or grill pan on your stovetop until very hot. Add the steaks and sear well. If you grill outside, use a grill mat so you don't lose your garlic pieces.
These are approximate times for doneness.
Place steaks on grill for 4-5 minutes initially so you get a good sear or char. Flip steaks over and continue to grill 3 to 5 minutes for medium-rare or internal temperature of 135 degrees. 5-7 minutes for medium or 140 degrees8 to 10 minutes for medium-well or 150 degrees.Once removed from the pan or grill, allow to rest for 10 minutes. Then slice against the grain of the meat.