Combine cornstarch and pepper together in a plastic storage bag. Add chicken and shake to coat.
Heat oil in large skillet over medium high heat.
Add chicken in single layer and cook on each side until brown, about 2 minutes each side.
Place chicken in slow cooker.
Combine soy sauce, vinegar, ketchup, sweet chili sauce, sugar, garlic, ginger and pepper flakes in a bowl. Pour over chicken.
I add my cashews half way through the baking timeso they don't get as soft but you can add them at the beginning if your prefer.
Cook on low for 3 - 4 hours (I did it for 3)
Serve over rice and garnish with green onion
Video
Notes
You could definitely add these veggies into the crockpot with the chicken or cook them separately and serve with it: Carrots Broccoli Red Bell Pepperand Green Bell Peppers Squash Zucchini Onion Cauliflower