Cut the chicken breasts in half crosswise, then arrange all the chicken pieces in one layer on a work surface. Sprinkle on both sides with 2 tablespoons each of the onion powder, seasoned salt, granulated garlic, kosher salt and black pepper.
In a shallow baking dish, combine the flour with the remaining 1 1/2 tablespoons onion powder, 1 tablespoon seasoned salt, 1 tablespoon granulated garlic, 1 tablespoon kosher salt and 1/2 tablespoon black pepper. Mix to blend.
Dredge the chicken pieces in the seasoned flour, tossing to coat thoroughly. Shake off excess flour and transfer the chicken to a wire rack set over baking sheet. Refrigerate for 30 to 60 minutes.
Fill a large Dutch oven by one-third with oil; heat over medium-high heat until the oil reaches 350 degrees F on a deep-fry thermometer. In batches, fry the chicken, flipping occasionally, until golden brown all over and the juices run clear, 10 to 12 minutes for white meat, 12 to 14 minutes for dark meat. Bring the oil back to temperature between batches. Serve hot.