Rinse the chicken breasts in cold water, then place them in a resealable plastic bag with the buttermilk and hot sauce. Close the bag, shake until the chicken pieces are fully coated, and refrigerate for at least 2 hours or overnight.
Position a rack in the center of the oven. Preheat the oven to 400°F. Spray a wire rack with vegetable oil spray and place it in a roasting pan or on a baking sheet.
Place the flour on a plate. Mix the cornflake crumbs, paprika, salt, black pepper, cayenne, garlic powder, onion powder, and poultry seasoning in a bowl until the ingredients are evenly distributed.
Remove the chicken breasts from the bag and place them on a plate. Pour the marinade into a medium bowl. Dredge each breast with the flour until fully coated, shaking off any excess. Then coat the chicken in the marinade, followed by a dredging in the cornflake mixture.
Arrange the chicken pieces on the prepared wire rack. Bake for 15 minutes. Reduce the oven temperature to 350°F and bake until cooked through and crispy, 15 to 20 minutes.