Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the chicken breast into uniform 1-inch cubes and place them in a bowl, tossing with avocado oil, sea salt, and black pepper.
Spread the seasoned chicken cubes across the baking sheet in a single layer and bake for 10 minutes.
While the chicken is in the oven, whisk together the orange juice, tamari, honey, arrowroot powder, minced ginger, minced garlic, and rice vinegar in a small bowl until smooth.
Remove the baking sheet from the oven and add the broccoli florets to the tray, then pour half of the prepared orange sauce over the chicken and broccoli.
Toss everything gently to coat and return the tray to the oven for another 10 to 12 minutes until the chicken is cooked through and the broccoli is tender-crisp.
Pour the remaining sauce into a small saucepan over medium heat and simmer for 2 minutes until it thickens into a glossy glaze.
Serve the baked chicken and broccoli over a bed of warm brown rice, drizzling with the extra thickened sauce and garnishing with sesame seeds.