Pat the chicken breast dry with a paper towel and cut into 1-inch cubes.
In a medium bowl, toss the chicken cubes with sea salt, black pepper, and arrowroot powder until evenly coated.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the skillet in a single layer and sear for 3-4 minutes per side until golden brown and crispy.
Remove the chicken from the pan and set aside on a plate.
In the same skillet, add the sliced red bell pepper and snap peas, sautéing for 3 minutes until tender-crisp.
Stir in the minced ginger, garlic, and pineapple chunks, cooking for another minute until fragrant.
Whisk together the coconut aminos and rice vinegar in a small bowl, then pour the mixture into the skillet.
Return the crispy chicken to the pan and toss everything together for 1-2 minutes until the sauce thickens and coats the ingredients.
Serve the stir-fry immediately over the warm cooked brown rice.