Step 1

Mix 2 tablespoons cornstarch, garlic powder, and ground ginger together in a small bowl. Toss chicken thighs in cornstarch mixture until they are evenly coated.

Step 2

Heat oil in a skillet over medium-high heat. Cook chicken in the skillet until browned on all sides, 3 minutes per side. Transfer to a plate and set aside.

Step 3

Drain juice from the can of pineapple chunks into a measuring cup. You should have approximately 3/4 cup to 1 cup of juice.

Step 4

Mix 1/2 cup pineapple juice, chicken stock, rice vinegar, brown sugar, ketchup, and soy sauce together in a slow cooker. Add browned chicken pieces and stir to coat chicken with the sauce. Cook on Low for 3 1/2 hours.

Step 5

Whisk remaining 2 tablespoons cornstarch with remaining 1/4 cup pineapple juice. Stir cornstarch mixture into the slow cooker. Increase the slow cooker heat to High and add pineapple chunks and chopped red bell pepper.

Step 6

Cook on High until the sauce is bubbly and thickened and bell pepper is crisp-tender, about 30 minutes. Garnish with chopped green onion.