Preheat the air fryer to 400°F (200°C) for about 3 minutes to ensure even cooking and crispy skin.
Pat the salmon fillets dry with paper towels to remove excess moisture, which helps achieve crispiness.
Lightly brush each fillet with olive oil or mayonnaise using a basting brush, coating the skin evenly to promote crisping and shine.
Sprinkle salt, pepper, and any optional herbs or spices evenly over the fillets, ensuring the seasoning adheres to the oily surface.
Place the fillets skin-side down into the air fryer basket, making sure they are not overcrowded to allow proper air circulation.
Cook for 8-10 minutes, listening for the satisfying crackle of the skin as it crisps up and turns a deep, golden brown.
Once cooked, carefully remove the fillets from the air fryer and transfer to a serving plate. Squeeze fresh lemon juice over the top to brighten the flavors.
Garnish with additional herbs if desired, and serve immediately to enjoy the crispy skin and tender interior.