Place the flank steak in a large ziplock bag. In a bowl, whisk together the remaining marinate ingredients. Pour the marinade into the bag with the flank steak. Close and refrigerate for at least 4 hours or overnight.
Heat grill to medium high heat. Add the flank steak and grill 5-7 minutes per side. Set aside and cover with foil. Let sit 10 minutes before slicing. Slice against the grain in long thin pieces.
Notes
Be careful not to overcook the meat. You want it to register about 130-135 degrees on a meat thermometer.
Let the meat sit, covered, for at least 5 minutes before cutting.
Cut the meat against the grain into thin strips.
Serve with corn or flour tortillas, and lots of toppings.