In a small bowl, whisk together soy sauce, honey, ketchup, olive oil, garlic, and black pepper. Pour over chicken.
Cover and cook on low heat for 4 hours or until chicken is cooked through.
Remove chicken from the slow cooker and slice or shred.
In a saucepan, heat the remaining liquid from the slow cooker over medium heat. Stir the cornstarch mixture and add to the saucepan. Cook until sauce thickens, about 2 minutes.
Serve chicken with thickened sauce, garnished with sesame seeds and green onions.
Notes
Adjust the sweetness by varying the amount of honey, according to taste.