Preheat oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Pat the chicken breast dry with a paper towel, cut into 1-inch cubes, and season with sea salt and black pepper.
In a small mixing bowl, whisk together the fresh orange juice, coconut aminos, sesame oil, grated ginger, minced garlic, and arrowroot powder until smooth.
Spread the chicken cubes and broccoli florets across the prepared baking sheet in a single layer.
Drizzle half of the orange sauce over the chicken and broccoli, tossing well to ensure every piece is coated.
Bake for 15 to 18 minutes, or until the chicken is cooked through and the broccoli reaches a tender-crisp texture.
While the chicken bakes, pour the remaining sauce into a small skillet over medium heat and simmer for 2-3 minutes until it thickens into a glossy glaze.
Divide the cooked brown rice into bowls, top with the baked chicken and broccoli, and finish with a drizzle of the thickened glaze.
Garnish with toasted sesame seeds and sliced green onions before serving warm.