Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized cubes and season evenly with sea salt and black pepper.
In a small mixing bowl, whisk together the orange juice, tamari, rice vinegar, honey, grated ginger, minced garlic, and arrowroot powder until the powder is fully dissolved.
Place the chicken cubes and broccoli florets on the prepared baking sheet, drizzle with toasted sesame oil, and toss to coat.
Pour half of the orange sauce mixture over the chicken and broccoli, tossing again to ensure everything is well-glazed.
Spread the mixture into a single layer and 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 over medium heat and simmer for 2 to 3 minutes until it thickens into a glossy syrup.
Serve the baked chicken and broccoli over the warm cooked brown rice, drizzling with the thickened sauce and garnishing with sesame seeds.