Place the chicken thighs in the crockpot insert and sprinkle salt and pepper on both sides.
In a medium sized bowl, combine honey, soy sauce, ketchup, oil, garlic, onion, and red pepper flakes. Stir to combine well. Pour over the chicken in the crockpot.
Cook on low for 3-4 hours or high for 1½-2½ hours.
When done, remove chicken from stock pot and cut into chunks. Prior to putting the chicken back in the stockpot, combine some cornstarch in water and whisk it into the crockpot to thicken up the sauce a bit (if the sauce doesn't thicken, it's ok - the liquid probably isn't hot enough to thicken it to the right consistency. It's ok if the sauce is more on the liquid side.) Throw the chicken back in and stir around to recoat the chicken in the sauce.
Serve hot over a bed of white rice (optional) and sprinkle some sesame seeds on top.