Marinate: up to 24 hours before grilling – the full 24 hours will net the most flavorAdd the grated garlic, balsamic vinegar, maple syrup and coconut aminos to a large ziplock baggie. Place the flank steak in the baggie and swoosh it around until all the surface areas are coated. Press the air out of the bag and place it on a plate in case there are any drips. Store it in the refrigerator until ready to use. You can do this the night before grilling, and then flip it over in the morning to make sure the other side gets its share of the marinade.
Grill it quickly on high heat. Flank tends to get chewier the longer it’s cooked, so cooking it to medium rare is ideal. Grill on high heat for about 4-6 minutes per side depending on the thickness - until an instant-read thermometer indicates it’s reached an internal temperature of 135-140° F. Taking it out of the refrigerator about 30 minutes before grilling will help it cook more evenly.
Let your steak rest for 5 to 10 minutes before cutting into it so the juices can redistribute.
Slice it against the grain. This is critical to keeping a cut like flank nice and tender.
To Serve: sprinkle liberally with flake salt. Add freshly ground pepper if you’d like.
Notes: I prefer Big Tree Farms brand coconut aminos (original). Look for a brand that only contains coconut nectar, water and salt. Coconut aminos is a great substitution for soy sauce if you’re adhering to a soy-free diet.