Special equipment: a deep-frying thermometer
Add the oil to a large, deep frying pan over high heat; heat to 350 degrees F on a deep-frying thermometer.
Generously sprinkle the chicken on both sides with some seasoning salt, then sprinkle with 1 teaspoon black pepper and the cayenne if using. Put the flour in a plastic or paper bag.
Two pieces at a time, add the chicken to the bag and shake until coated in flour. Shake off the excess flour and place the chicken in the hot oil. Fry until golden brown, 8 minutes per side. Transfer to a paper-towel-lined plate to absorb the excess oil.