Chop chicken into 2 inch pieces. Add to a large resealable bag and add corn starch. Seal and shake to coat chicken.
Drizzle a large skillet with the oil and preheat over medium-high heat. Add chicken and saute 1-2 minutes (just to brown the very outside, chicken should not be cooked through) and remove from heat. Add to a greased slow cooker.
Whisk together the cold water and corn starch til dissolved. Add soy sauce, sesame oil, honey, garlic, ketchup, and rice vinegar and whisk to combine.
Poor sauce over the chicken. Cover and cook on low 3 hours. Serve over cooked rice and garnish with sesame seeds if desired.
Pro tip: Add 1/2 teaspoon crushed red pepper flakes for a bit of heat!