Dice the chicken breast into 1-inch cubes and toss in a bowl with arrowroot powder, sea salt, and black pepper until evenly coated.
Heat the avocado oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the chicken to the pan in a single layer and sear for 3-4 minutes per side until the edges are golden and crispy.
Remove the chicken from the pan and set aside on a plate; add the broccoli, sliced bell pepper, and snap peas to the same pan.
Stir-fry the vegetables for 3-5 minutes until tender-crisp, then add the minced ginger and garlic, cooking for another 30 seconds until fragrant.
In a small bowl, whisk together the tamari, toasted sesame oil, and rice vinegar.
Return the chicken to the pan, pour the sauce over the mixture, and toss for 1 minute until the sauce thickens and coats everything.
Transfer to a plate and garnish with toasted sesame seeds before serving.