For the chicken: Combine the flour and black pepper in large Ziploc bag. Add the chicken and 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.
FOR THE SAUCE: Note: If you like it really saucy over rice, consider doubling the sauce. Combine soy sauce, vinegar, ketchup, sugar, garlic, ginger, and pepper flakes in small bowl; pour over chicken. Cook on LOW for 3-4 hours. Add cashews and stir. Serve over white rice.
INSTANT POT INSTRUCTIONS: Combine sauce in step two and add to the instant pot. Add the chicken and toss to coat. Lock the lid and turn valve to "sealing". Set the manual/pressure cook button to 6 minutes on high pressure. Turn the valve to venting. After pressure has released, remove the lid. In a small bowl, make a slurry with 1 tablespoon cornstarch and 1 tablespoon water. Stir into the instant pot and turn on the Sautee function for 2-3 minutes or until sauce thickens. Add cashews and stir. Serve over rice. Garnish with green onions or chopped cilantro if desired.
Notes
The sauce should be doubled if you want plenty to pour over rice.Note: I don't use ginger a lot so to buy fresh ginger for just a small amount isn't reasonable. My grocery store sells pureed ginger in a tube that lasts longer and you can use it as you need. Or you can freeze your fresh ginger.