Prep the chicken: Pat chicken thighs dry with paper towels. This step helps the skin crisp. Trim excess skin or fat if needed.
Make the garlic herb rub: In a small bowl, combine 2 tablespoons olive oil, 4 minced garlic cloves, 1 teaspoon lemon zest, 1 tablespoon lemon juice, 1 tablespoon chopped fresh parsley, 1 teaspoon chopped fresh thyme (or 1/2 teaspoon dried), 1 teaspoon smoked paprika, 1 teaspoon kosher salt, 1/2 teaspoon black pepper, and 1/2 teaspoon onion powder.
Add a pinch of red pepper flakes if you like heat.
Season generously: Rub the mixture under the skin where possible and all over the surface of each thigh. Getting some seasoning under the skin intensifies flavor.
Preheat the air fryer: Set it to 380°F (193°C) for 5 minutes. A preheated basket helps the skin crisp faster.
Arrange in the basket: Lightly spray the basket.
Place thighs skin-side down in a single layer with a little space between each. Avoid overcrowding; work in batches if needed.
Air fry, then flip: Cook at 380°F for 12 minutes. Flip the thighs to skin-side up and cook another 10–12 minutes, until the skin is crisp and the internal temperature hits 175–185°F in the thickest part (thighs are more forgiving and juicier above 165°F).
Optional final crisp: For extra crackly skin, cook 2–3 additional minutes at 400°F.
Watch closely to prevent over-browning.
Rest and serve: Let the chicken rest for 5 minutes. Squeeze a bit of lemon over the top and scatter extra chopped parsley before serving.