1. Arrange potatoes in the bottom of the slow cooker. Season chicken with salt and pepper; place on top.
2. Whisk together garlic, honey, soy sauce, vinegar, and sriracha (if using). Pour over chicken and potatoes.
3. Cook on LOW 4–5 hours or HIGH 2–3 until potatoes are tender and chicken is cooked through.
4. Whisk cornstarch with water; stir into the cooker. Cover and cook 10–15 minutes more to thicken.
5. Spoon onto plates and finish with sliced green onions and sesame seeds. Spoon extra sauce over everything.