In a large zip-top bag or shallow dish, whisk together all marinade ingredients.
Add the flank steak and coat thoroughly.
Seal and refrigerate overnight (at least 8 hours, up to 24).
Preheat grill to high heat (around 450 - 500°F).
Remove steak from marinade and let it come to room temp for 20 - 30 minutes.
Discard leftover marinade.
Grill steak for 4 - 6 minutes per side, depending on thickness and desired doneness.
Aim for medium-rare (130 - 135°F).
Remove from grill and rest for 5 - 10 minutes.
Slice against the grain into thin strips.
