Place the chicken breast in a bowl with the buttermilk and marinate for at least 30 minutes in the refrigerator.
In a shallow dish, whisk together the almond flour, arrowroot powder, smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, allowing any excess to drip off, then dredge it thoroughly in the flour mixture until well coated.
Lightly coat the air fryer basket with avocado oil spray and place the chicken inside.
Air fry at 375°F for 12-15 minutes, flipping halfway through and applying another light spray of oil, until the exterior is crisp and the internal temperature reaches 165°F.
While the chicken cooks, steam the green beans until tender-crisp and serve immediately alongside the hot chicken.