Place the chicken breast between two sheets of parchment paper and pound with a meat mallet until it is an even half-inch thickness.
In a shallow bowl, soak the chicken in the buttermilk for at least 15 minutes to tenderize.
In a separate shallow dish, whisk together the almond flour, arrowroot powder, smoked paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, and dredge thoroughly in the flour mixture, pressing to adhere.
Lightly coat the air fryer basket with avocado oil and place the chicken inside. Lightly spray the top of the chicken with the remaining oil.
Air fry at 375°F for 12-15 minutes, flipping halfway through, until the coating is golden brown and the internal temperature reaches 165°F.
Toast the whole grain bun lightly in a dry pan or the air fryer for 1 minute.
Spread the avocado oil mayonnaise on the bottom bun, then layer with butter lettuce, the crispy chicken, and dill pickles before closing the sandwich.