Remove the chicken thighs from the refrigerator 15-20 minutes before cooking. Pat every piece completely dry with paper towels, top and bottom.
Stir together the kosher salt, garlic powder, onion powder, smoked paprika, black pepper, dried thyme, and cayenne. Drizzle the olive oil and lemon juice over the thighs and rub all over. Sprinkle the seasoning mix evenly over every thigh, front and back, pressing gently.
Position a rack in the center of the oven and preheat to 425°F (220°C). Line a rimmed sheet pan with foil, set a wire rack inside, and arrange the seasoned thighs skin-side up with space between each.
Bake for 30-35 minutes until the skin is deep golden brown and crackly. The thighs are done when an instant-read thermometer reads at least 165°F (74°C) in the thickest part, avoiding the bone.
Transfer the baked thighs to a clean plate and let them rest for 5 minutes.
Serve hot with pan juices spooned over, garnished with fresh thyme or parsley and lemon wedges.