DO-AHEAD TIP: Marinate beef overnight or for at least 8 hours. If using bamboo skewers, presoak them in water for 30 minutes, to prevent burning on grill.
Slice meat across the grain (diagonally) into 1/4-inch strips. Place in a large zipper-topped plastic bag. In a small bowl, whisk together next 5 ingredients (teriyaki sauce through crushed red pepper flakes). Pour mixture over steak strips.
Seal bag and turn to coat. Refrigerate overnight or for at least 8 hours, turning several times. Preheat grill to MEDIUM. Toast sesame seeds: In a small skillet, cook sesame seeds over medium heat for 3 to 4 minutes or until fragrant, shaking occasionally. Prepare rice.
Meanwhile, weave steak strips onto skewers (discarding marinade and bag). Place steak skewers on the grill. Cover and cook for 2 to 4 minutes per side, or until they reach desired level of doneness. Sprinkle skewers with toasted sesame seeds and serve over hot rice. Enjoy!