Place the chicken pieces in a single layer at the bottom of the slow cooker.
In a medium mixing bowl, whisk together soy sauce, honey, rice vinegar, ginger, garlic, and black pepper until well combined.
Pour the sauce mixture over the chicken in the slow cooker.
Cover and cook on low for 4 to 5 hours or on high for 2 to 3 hours until chicken is tender.
Remove the chicken from the slow cooker and shred with two forks or slice into strips.
In a small bowl, whisk the cornstarch and cold water together to create a smooth slurry.
Pour the slurry into the slow cooker liquid and whisk to combine.
Set the slow cooker to high and cook for an additional 10 to 15 minutes until the sauce has thickened to a glaze consistency.
Return the chicken to the slow cooker and toss to coat thoroughly in the sauce.
Serve over rice, garnished with sesame seeds and sliced green onions.