Prep the oven and pan. Preheat the oven to 425°F (220°C). Line a sheet pan with foil and place a wire rack on top. This keeps the chicken elevated so the skin crisps evenly.
Pat the chicken very dry. Use paper towels to thoroughly dry the thighs, especially the skin. Dry skin = crisp skin.
Mix the seasoning. In a small bowl, combine salt, pepper, garlic powder, paprika, onion powder, baking powder, and any optional herbs.
Oil and season. Drizzle the thighs with oil on both sides.
Sprinkle the seasoning mix all over, focusing on the skin. Gently press to help it adhere.
Arrange for airflow. Place the thighs skin-side up on the rack. Leave a bit of space between each piece so hot air can circulate.
Roast until crisp and cooked through. Bake for 35–45 minutes, depending on size.
The skin should be deeply golden and crackly. An instant-read thermometer should read 165°F (74°C) in the thickest part without touching bone.
Optional blast for extra crisp. If you want more browning, broil on high for 1–2 minutes. Watch closely to avoid burning.
Rest and finish. Let the chicken rest 5 minutes.
Squeeze a little lemon over the top and sprinkle with parsley if you like. Serve hot.