Remove tough stems, tear leaves into 2-inch pieces and dry them completely.
Preheat the air fryer to 325°F for 3 minutes.
Add oil to the kale and massage with fingertips until each leaf has a faint sheen. Add salt and optional seasoning.
Place a loose single layer in the basket. Use an approved rack only if the manufacturer permits it and leaves tend to lift.
Air fry 3 minutes, shake gently, then cook 1 to 3 minutes more. Remove crisp pieces as they finish.
Spread on a rack or plate for 3 minutes; the leaves become crisper as steam escapes.