In a small bowl, whisk together the tamari, rice vinegar, honey, sesame oil, minced ginger, garlic, and red pepper flakes to create the sauce.
Pat the chicken breast dry and cut into 1-inch cubes, then toss in a bowl with arrowroot powder, sea salt, and black pepper until lightly coated.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the chicken to the skillet and sear for 5-6 minutes, turning occasionally until golden brown and cooked through.
Remove the chicken from the pan and set aside.
Add the broccoli florets and red bell pepper to the same skillet with a splash of water, covering for 2 minutes to steam until tender-crisp.
Return the chicken to the skillet and pour the sauce over the mixture.
Stir-fry for 1-2 minutes until the sauce thickens and coats the chicken and vegetables beautifully.
Serve the stir-fry over the warm cooked brown rice and garnish with fresh green onions.