Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Dice the chicken breast into 1-inch cubes and season evenly with sea salt and black pepper.
In a small mixing bowl, whisk together the orange juice, tamari, honey, sesame oil, minced garlic, grated ginger, and arrowroot powder until smooth.
Arrange the seasoned chicken cubes and broccoli florets on the prepared baking sheet in a single layer.
Drizzle exactly half of the orange sauce over the chicken and broccoli, tossing gently with tongs to ensure everything is coated.
Bake for 15-18 minutes, or until the chicken is cooked through and the broccoli reaches a crisp-tender texture.
While the chicken bakes, pour the remaining sauce into a small saucepan and simmer over medium heat for 2-3 minutes until it thickens into a glossy glaze.
Remove the tray from the oven, toss the baked chicken in the thickened glaze, and serve immediately over the warm brown rice.
Garnish with sesame seeds and sliced green onions for a fresh pop of flavor.