Season both sides of chicken with salt and pepper to taste; transfer to the slow cooker.
In a medium bowl, whisk together the diced onion, garlic, honey, soy sauce, ketchup, vegetable oil, and red pepper flakes. Pour over chicken.
Put the lid on and cook on low. Whenever we make this, they're done at 4 hours, but we recommend checking after 3 hours to make sure the chicken doesn't dry out. Most importantly, they're done when an internal temperature of the thighs reaches 165 degrees F.
With a slotted spoon, transfer chicken to a plate and keep warm.
In a small bowl, whisk together the water and cornstarch until dissolved. Pour mixture into a small saucepan along with the sauce. Whisk to combine and cook over medium heat until bubbly and thickened.
Serve chicken thighs over cooked rice and spoon some sauce on top.
Sprinkle with a little sesame seeds and diced scallions.
NOTE: We prefer chicken thighs over chicken breasts, since dark meat is more moist and flavorful, but chicken breasts are fine. They won't need as much time to cook, so start checking on them sooner.Don't have a crock pot? Try using a roasting pan and cook in a 250 degree F oven for 3-4 hours, or until an internal temperature of 165 degrees is reached.
Nutritional information given is an automatic calculation and can vary based on the exact products you use and any changes you make to the recipe. If these numbers are very important to you, I would recommend calculating them yourself.