Cover chicken with buttermilk in a large bowl; refrigerate at least 2 hours or overnight.
Mix flour, seasoned salt, pepper, paprika, garlic powder, and cayenne in a shallow dish.
Heat oil in a large deep skillet or Dutch oven to 350°F.
Remove chicken, letting excess buttermilk drip off; dredge thoroughly in seasoned flour.
Briefly dip in buttermilk again, then flour for a thick coating.
Carefully add chicken skin-side down without crowding; work in batches if needed.
Fry 12-15 minutes per side until golden brown and center reaches 165°F.
Drain on a wire rack over a baking sheet; rest 5 minutes before serving.