Slice the beef flank steak against the grain into 1/4-inch strips. Toss strips with Teriyaki Sauce and marinate for 1 hour.
Preheat grill to high heat. Clean and grease the grill grates. Thread beef strips onto metal skewers or wooden skewers soaked in water to prevent burning.
Grill skewers for 2-3 minutes on each side until lightly charred and cooked through: 145F. Garnish with sesame seeds and sliced scallions if desired.
