Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the chicken breast into bite-sized 1-inch cubes and place them in a large mixing bowl with the broccoli florets.
In a small bowl, whisk together the orange juice, orange zest, tamari, rice vinegar, honey, minced garlic, grated ginger, arrowroot powder, and sesame oil until smooth.
Season the chicken and broccoli with sea salt, black pepper, and red pepper flakes, then pour half of the orange sauce over the mixture and toss to coat thoroughly.
Spread the chicken and broccoli in a single layer on the prepared baking sheet and bake for 15 to 18 minutes, or until the chicken is cooked through and the broccoli is tender.
While the chicken bakes, pour the remaining orange sauce into a small saucepan over medium heat and simmer for 2 to 3 minutes until it thickens into a glossy glaze.
Remove the tray from the oven, drizzle the thickened glaze over the chicken and broccoli, and serve immediately over the warm cooked brown rice.