Preheat oven to 400°F and line a large baking sheet with parchment paper.
Cut the chicken breast into one-inch bite-sized pieces and season evenly with sea salt and black pepper.
In a small mixing bowl, whisk together the fresh orange juice, tamari, honey, rice vinegar, arrowroot powder, minced garlic, grated ginger, and sesame oil until smooth.
Arrange the chicken pieces and broccoli florets in a single layer on the prepared baking sheet.
Pour half of the orange sauce over the chicken and broccoli, tossing gently to ensure every piece is well-coated.
Bake for 15 to 18 minutes, or until the chicken is cooked through and the broccoli is tender-crisp.
While the chicken bakes, pour the remaining sauce into a small saucepan and simmer over medium heat for 3-5 minutes until it thickens into a glossy glaze.
Drizzle the thickened sauce over the baked chicken and broccoli, sprinkle with sesame seeds, and serve immediately over the warm cooked brown rice.