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 chop the broccoli into small, uniform florets.
In a small mixing bowl, whisk together the orange juice, orange zest, tamari, honey, rice vinegar, minced garlic, grated ginger, arrowroot powder, sesame oil, and red pepper flakes.
Place the chicken and broccoli on the prepared baking sheet, then pour the orange sauce over them, tossing well to ensure every piece is thoroughly coated.
Season the mixture with sea salt and black pepper, then spread it into a single layer to ensure even roasting.
Bake for 18-20 minutes, or until the chicken is cooked through and the sauce has thickened into a glossy glaze.
Remove from the oven and garnish with sesame seeds and thinly sliced green onions before serving.