01 - Place chicken thighs or breasts in the bottom of the slow cooker, ensuring even distribution for consistent cooking.
02 - Whisk together pineapple juice, soy sauce, brown sugar, ketchup, rice vinegar, minced garlic, and grated ginger in a medium bowl until sugar dissolves completely.
03 - Pour the sauce mixture evenly over the chicken. Layer sliced onion, bell pepper pieces, and pineapple chunks on top.
04 - Cover and cook on LOW setting for 4 to 5 hours, or until chicken reaches internal temperature of 165°F and is fork-tender.
05 - Remove chicken and vegetables to a serving platter using tongs or a slotted spoon. Cover loosely with foil to retain heat.
06 - Mix cornstarch and water in a small bowl until smooth, ensuring no lumps remain.
07 - Transfer cooking liquid from slow cooker to a saucepan. Bring to simmer over medium heat, whisk in cornstarch slurry, and cook for 2 to 3 minutes until sauce coats the back of a spoon.
08 - Pour thickened sauce over chicken and vegetables. Garnish with sliced green onions and sesame seeds. Serve immediately over steamed rice.