Whisk together all the marinade ingredients in a small bowl.
Add flank steak to a resealable bag and pour marinade into the bag and seal. Place in the refrigerator for 30 minutes or up to 8 hours.
Preheat your smoker to 225°F and place the flank steak directly on the grates and smoke for 1 ½ hours or until the steak reaches an internal temperature of 130-135°F.
Allow steak to rest for 15 minutes then serve sliced into thin strips.