In a mixing bowl add the chicken and cornstarch. Toss until the chicken is completely coated in the cornstarch. In a medium sized skillet over medium high heat add oil and cook the chicken until the chicken is lightly brown but not cooked throughout. Put in the bottom of a slow cooker.
If you are cooking the chicken without browning in the skillet first, when chicken is finished cooking, remove the chicken and add 1 Tablespoon cornstarch to the sauce. Add the chicken back to the crockpot and cook for an additional 15 minutes until the sauce thickens up. Chicken could also take longer to cook, closer to 4 hours.