Place the chicken thighs in the slow cooker. In a separate bowl, whisk together honey, soy sauce, ketchup, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes. Pour the mixture over the chicken.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender.
Once cooked, remove the chicken from the slow cooker and shred it using two forks.
In a small bowl, mix the cornstarch and water to create a slurry. Stir this into the sauce in the slow cooker and cook on high for an additional 15-20 minutes, until the sauce thickens.
Return the shredded chicken to the slow cooker and stir to coat it in the thickened sauce.
Serve the chicken over rice or noodles, garnished with sesame seeds and sliced green onions.