Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized cubes and place them in a bowl with the broccoli florets.
Toss the chicken and broccoli with avocado oil, sea salt, and black pepper until evenly coated.
Spread the mixture in a single layer on the prepared baking sheet and bake for 15-18 minutes until the chicken is cooked through.
While the chicken bakes, whisk together orange juice, orange zest, coconut aminos, rice vinegar, honey, minced garlic, grated ginger, and arrowroot powder in a small saucepan.
Simmer the sauce over medium-low heat for 3-5 minutes, stirring constantly until it thickens into a glossy glaze.
Remove the chicken and broccoli from the oven, transfer to a large bowl, and pour the warm orange glaze over the top.
Toss gently to coat and garnish with sesame seeds and sliced green onions before serving.