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 evenly coated.
In a small glass jar, whisk together the fresh orange juice, tamari, grated ginger, and minced garlic to create the glaze.
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 until golden brown and crispy on all sides.
Toss in the broccoli florets and sliced red bell pepper, stir-frying for another 3 minutes until the vegetables are vibrant and crisp-tender.
Pour the orange glaze and sesame oil over the chicken and vegetables, stirring constantly for 1-2 minutes until the sauce thickens and coats everything beautifully.
Serve the stir-fry immediately over the warm cooked brown rice and garnish with toasted sesame seeds and sliced green onions.