Cut the chicken breasts into bite-size pieces.
Seed and dice the red bell pepper into 1-inch pieces.
Drain and reserve the pineapple juice from canned pineapple chunks in a small bowl. With the pineapple juice, add the chicken stock, brown sugar, soy sauce and minced garlic.
Place the chicken pieces and red bell pepper pieces in the base of the slow cooker and pour the pineapple chunks around the chicken. Season with a sprinkle of salt and pepper. Pour the pineapple-soy sauce mixture over the top.
Set on low and cook for 8 hours. With 30 minutes left in the cooking cycle, swirl the cornstarch with a few Tbsp of water and stir it into the sauce. Cook for 30 more minutes to allow sauce to thicken. Garnish with sesame seeds, if desired.
Cook the rice as directed.
Serve Slow Cooker Sweet & Sour Chicken over rice with side of veggies.