In a bowl, combine the chicken thighs, buttermilk, and hot sauce if using. Cover and refrigerate for at least 1 hour, preferably longer for more flavor.
In another bowl, mix the flour with paprika, garlic powder, onion powder, cayenne, salt, and pepper.
Remove the chicken from the buttermilk, letting excess drip off. Dredge each thigh in the seasoned flour, pressing firmly to ensure a thick, even coating.
Heat about 1–2 inches of vegetable oil in a heavy skillet over medium heat to 350°F (175°C). Fry the chicken thighs in batches, about 4–5 minutes per side, until golden brown and cooked through.
Spread mayonnaise or your favorite sauce on the bottom bun, add lettuce, a fried chicken thigh, tomato slices, pickles, and the top bun.