Step 1: Prepare the Marinade

In a medium bowl, whisk together the pineapple juice, soy sauce, ketchup, brown sugar, rice vinegar, Worcestershire sauce, grated ginger, minced garlic, sesame oil, black pepper, and red pepper flakes. Stir until the sugar is fully dissolved, creating a well-balanced marinade.

Step 2: Marinate the Chicken

Place the chicken pieces in a large zip-top bag or a shallow dish. Pour the marinade over the chicken, ensuring each piece is well coated. Seal the bag or cover the dish and refrigerate for at least 4 hours, but preferably overnight for the best flavor absorption.

Step 3: Prepare the Grill

If using a charcoal grill, light the coals and let them turn white-hot before grilling. If using a gas grill, preheat to medium-high heat. For an indoor grill pan, preheat over medium-high heat and lightly grease with vegetable oil.

Step 4: Grill the Chicken

Remove the chicken from the marinade and shake off excess liquid. Reserve the marinade for basting. Place the chicken on the grill and cook for about 5-7 minutes per side. Baste frequently with the reserved marinade, flipping occasionally to achieve a beautiful glaze and deep caramelization. The internal temperature should reach 165°F (75°C).

Step 5: Rest and Serve

Once cooked, transfer the chicken to a plate and let it rest for 5 minutes. Garnish with chopped green onions and sesame seeds before serving.