Preheat the air fryer to 380°F for 5 minutes; apply a light coating of cooking spray if preferred.
Place the chicken thighs in a large zip-top bag or a lidded bowl. Add the kosher salt, garlic powder, smoked paprika, onion powder, and oregano. Seal and shake vigorously to evenly distribute the seasoning.
Transfer the thighs to the air fryer basket, arranging them skin side down. Cook for 12 minutes.
Flip the chicken thighs to skin side up and continue cooking for an additional 10 to 15 minutes. For extra crispiness, extend the cooking time in 4-minute intervals until the desired texture is reached.
Ensure doneness by confirming that an internal meat thermometer inserted into the thickest part registers 165°F. Cooking time may differ based on thigh size and air fryer model. Serve immediately.