In a medium-sized bowl, toss chicken in cornstarch to coat.
In large skillet, heat oil over medium high heat, then add chicken and brown. You don't need to cook the chicken through, just get color on each side.
Place the browned chicken in the slow cooker.
In a small mixing bowl combine the hot wing sauce, brown sugar, water, and vinegar.
Pour the sauce over the chicken in the slow cooker and stir.
Cook on low for 4 hours, stirring once or twice to make sure the sugars are not burning.
Garnish with scallions and serve over white rice.