Place the chicken thighs in the slow cooker, ensuring they are spread out evenly.
In a medium bowl, whisk together soy sauce, honey, rice vinegar, sesame oil, minced garlic, and grated ginger.
Pour the teriyaki sauce mixture over the chicken in the slow cooker, ensuring the chicken is well-coated.
Cover the slow cooker and set it to low, cooking for 6 hours. If you're short on time, set it to high for about 3 hours.
When cooking time is done, check the chicken. If you'd like a thicker sauce, mix the cornstarch with water in a small bowl and stir it into the sauce. Let it cook for an additional 15 minutes on high to thicken.
Shred the chicken using two forks and stir it back into the sauce.
Serve over cooked rice, garnished with chopped green onions and sesame seeds.