Place the chicken breast in a shallow bowl and pour the buttermilk over it, letting it marinate for at least 15 minutes.
In a separate bowl, whisk together the almond flour, arrowroot powder, smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge it thoroughly in the flour mixture until fully coated.
Lightly coat 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 degrees Fahrenheit for 12-15 minutes, flipping halfway through, until the exterior is golden and crispy.
While the chicken cooks, stir together the Greek yogurt and Dijon mustard in a small bowl to create a clean-eating spread.
Toast the sprouted grain bun and assemble the sandwich with the sauce, chicken, lettuce, and pickles.