Place the chicken breast between two sheets of parchment paper and pound to an even half-inch thickness.
Place the chicken in a shallow bowl and pour the buttermilk over it, ensuring it is fully submerged; marinate for at least 15 minutes.
In a separate shallow dish, whisk together the almond flour, arrowroot starch, garlic powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge thoroughly in the flour mixture, pressing to adhere.
Lightly spray the air fryer basket with avocado oil, place the chicken inside, and 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 sprouted grain bun lightly in the air fryer or a toaster.
Assemble the sandwich by placing the lettuce, tomato, and pickles on the bottom bun, topping with the crispy chicken, and finishing with the top bun.