Optionally, line a 6-quart or 7-quart slow cooker with a liner for easy cleanup.
Drizzle 1 tablespoon of olive oil at the bottom of the slow cooker or liner.
In a large ziptop bag, combine chicken, cornstarch, salt, and pepper.
Seal and shake to coat the chicken.
Transfer the chicken into the slow cooker, spreading it evenly.
In a 2-cup measuring cup or medium bowl, mix the orange marmalade, soy sauce, rice wine vinegar, sesame oil, ginger, garlic, and the remaining tablespoon of olive oil.
Stir the mixture until fully combined.
Pour the sauce evenly over the chicken, ensuring all pieces are well-coated.
Cover and cook on high for about 2 hours, or low for about 4 hours, checking for doneness with a thermometer (165°F).
Once done, transfer the chicken to a plate, adding the cooking sauce over the top.
Garnish with sesame seeds, green onions, and optional orange wedges before serving.
The crockpot orange chicken is reddy to be served. Enjoy!