Cut the chicken breast into bite-sized 1-inch cubes.
In a small bowl, whisk together the tamari, rice vinegar, honey, arrowroot powder, minced ginger, minced garlic, and red pepper flakes to create the sauce.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the chicken cubes to the skillet and sear until golden brown and cooked through, about 5-6 minutes.
Remove the chicken from the pan and set aside.
Add the broccoli florets and sliced red bell pepper to the same skillet, adding a splash of water if needed to steam-fry until tender-crisp.
Return the chicken to the skillet and pour the sauce over the mixture.
Stir constantly for 1-2 minutes until the sauce thickens and coats the chicken and vegetables evenly.
Serve the stir-fry over the warm cooked brown rice and garnish with sesame seeds.