Trim the woody base off each 4 large king trumpet (king oyster) mushrooms.
Using a mandolin, slice lengthwise along the stem into thin, even strips about 1/16 inch (2mm) thick — thin enough to crisp, but not so thin they vanish.
Use the mandolin's guard hand-piece for safety or use a metal safety glove.
Make the marinade: In a shallow dish or zip-top bag, whisk together 3 tablespoons tamari or coconut aminos, 1 tablespoons toasted sesame oil, 1 tablespoons maple syrup, 1 teaspoons smoked paprika, 1 teaspoons olive oil, 0.3 teaspoons black pepper, and 1 teaspoons rice vinegar until combined
Marinate the strips: Add the mushroom strips to the marinade, tossing gently so every piece is coated. Let sit for at least 15 minutes.
Oven method: arrange and bake: Preheat oven to 350°F. Lay the marinated strips in a single layer on a parchment-lined baking sheet, without overlapping. Bake for 20 minutes, then flip each strip. Continue baking for another 10-15 minutes, watching closely near the end, until the edges are deep brown and crisp while the centers stay slightly chewy. They'll crisp further as they cool.
Air fryer method: arrange and cook: Preheat the air fryer to 360°F. Arrange strips in a single layer in the basket, working in batches if needed so pieces don't overlap. Cook for 8 minutes. Flip each strip and continue cooking for another 4-6 minutes, checking every couple minutes near the end, until deeply browned and crisp at the edges.
Cool and serve: Transfer to a wire rack or plate and let cool for 5 minutes — this is when they crisp up the most. Serve on sandwiches, salads, or eat straight off the rack.