Mince the Garlic (3 clove).
Chop the Fresh Thyme (1 tablespoon).
In a small bowl, mix together the packed Brown Sugar (1/4 cup), Bourbon (1/4 cup), Olive Oil (1/4 cup), Tamari Soy Sauce (1/2 cup), fresh thyme, garlic, and Crushed Red Pepper Flakes (1/4 teaspoon). Pour into a resealable plastic food storage bag.
Place Flank Steak (1.5 pound) in the bag, remove as much air as possible, and seal. Flip the steak around a few times to coat with marinade. Place in the refrigerator for at least two hours and up to eight. Flip and rotate every few hours.
Heat barbecue or grill to medium high heat. Remove steak from marinade, and blot off the excess moisture with a paper towel. Place steak on the hot grill. Cook for 5-6 minutes on the first side for medium rare. Flip and cook an additional 5-6 minutes.
Transfer flank steak to a cutting board, and allow it to rest for 5 minutes so that the juices redistribute throughout the meat. Thinly slice, going against the grain, at about a 35-45 degree angle.