Cut the chicken breast into 1-inch bite-sized pieces and season evenly with sea salt and black pepper.
In a small glass bowl, whisk together the orange juice, coconut aminos, rice vinegar, minced fresh ginger, minced garlic, and arrowroot powder until no clumps remain.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken pieces to the hot skillet in a single layer and cook for 5-6 minutes, turning occasionally, until golden brown and cooked through.
Add the broccoli florets to the skillet along with 2 tablespoons of water, then immediately cover with a tight-fitting lid to steam for 2-3 minutes until tender-crisp.
Remove the lid and pour the prepared orange sauce mixture over the chicken and broccoli.
Stir constantly for 1-2 minutes as the sauce bubbles and thickens into a glossy glaze that coats every piece.
Garnish with sliced green onions and sesame seeds before serving immediately.