Dice the chicken breast into 1-inch bite-sized pieces and season with sea salt and black pepper.
In a small bowl, whisk together the fresh orange juice, tamari, rice vinegar, honey, and arrowroot powder until the starch is fully dissolved.
Heat avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the skillet and cook for 5-6 minutes, stirring occasionally, until golden brown and cooked through.
Remove the chicken from the pan and set aside; immediately add the broccoli florets and a splash of water to the pan, covering with a lid for 2 minutes to steam-sauté.
Remove the lid and stir in the minced garlic, grated ginger, and red pepper flakes, cooking for 30 seconds until fragrant.
Return the cooked chicken to the pan and pour the orange sauce mixture over the chicken and broccoli.
Simmer for 1-2 minutes, stirring constantly, until the sauce thickens into a glossy glaze that coats every piece.
Remove from heat, drizzle with toasted sesame oil, and garnish with thinly sliced green onions before serving warm.