In a small glass bowl, whisk together the tamari, rice vinegar, honey, arrowroot powder, and red pepper flakes until the arrowroot is fully dissolved.
Heat the avocado oil in a large stainless steel skillet or wok over medium-high heat until shimmering.
Add the cubed chicken breast in a single layer, searing for 3-4 minutes without moving them to develop a golden-brown crust.
Flip the chicken and cook for another 2 minutes, then remove the chicken from the pan and set aside on a plate.
In the same pan, add the broccoli florets and sliced bell peppers, sautéing for 3 minutes until they are bright and tender-crisp.
Stir in the minced ginger and garlic, cooking for just 30 seconds until fragrant to avoid burning.
Return the chicken and any accumulated juices to the skillet, then pour the sauce mixture over the top.
Toss everything together for 1-2 minutes until the sauce bubbles and thickens into a glossy, sticky glaze that coats every piece.
Remove from heat, drizzle with toasted sesame oil, and serve immediately over the warm brown rice garnished with fresh green onions.