Place the chicken breast in a bowl and cover with buttermilk, marinating for at least 30 minutes in the refrigerator.
In a shallow dish, whisk together the almond flour, half of the arrowroot powder, garlic powder, onion powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, allowing excess to drip off, then dredge thoroughly in the almond flour mixture, pressing to ensure an even coating.
Mist the chicken with avocado oil and place in an air fryer at 375°F for 12-15 minutes, flipping halfway through, until the exterior is golden and the internal temperature reaches 165°F.
While the chicken cooks, combine the chicken bone broth and whole milk in a small saucepan over medium heat.
Whisk the remaining arrowroot powder with a splash of water to create a slurry, then stir it into the simmering broth until the gravy thickens.
Stir in the fresh thyme and pour the warm gravy over the crispy chicken before serving.