Combine flour and pepper in large Ziploc bag. Add chicken. Shake to coat with flour mixture.
Heat oil in skillet over medium-high heat. Brown chicken about 2 minutes on each side.
Place chicken in slow cooker.
Combine soy sauce, vinegar, ketchup, sugar, garlic, ginger, and pepper flakes in small bowl; pour over chicken.
Cook on LOW for 3 to 4 hours.
Add cashews and stir.
Serve over rice.
