Chopped scallions and cooked white rice, for serving
Coat the insert of a 6-quart slow cooker with cooking spray and add the chicken thighs.
In a glass measuring cup, whisk together the honey, ketchup, soy sauce, oregano, pepper flakes, garlic and ginger and pour over the chicken.
Cover and cook on low until the chicken is cooked through and tender, 5 to 6 hours. Turn off the heat, uncover and let rest for about 10 minutes before serving.
The chicken and sauce can be served as-is or, for a thicker sauce, remove the chicken and set aside, covered, to keep warm, then turn the slow cooker to high.
Stir the cornstarch and 2 tablespoons cold water together until it resembles heavy cream. Pour the mixture into the sauce, cover and cook until the sauce is thick and bubbling, about 30 minutes. (The mixture must come to a boil to activate the starch and thicken the sauce.) Return the chicken back to the sauce and heat the chicken through, about 5 minutes.
Transfer the chicken and sauce to a platter, sprinkle with the sesame seeds and scallions and serve hot with rice.