Whisk the coconut aminos, minced fresh ginger, minced garlic, and arrowroot powder in a small bowl to create the stir-fry sauce.
Slice the flank steak against the grain into thin strips and season evenly with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over high heat until it begins to shimmer.
Add the beef strips in a single layer and sear for 2 minutes until browned and slightly crispy on the edges, then remove from the pan and set aside.
Add the broccoli florets to the same pan with a splash of water, covering immediately for 2 minutes to steam-fry until tender-crisp.
Return the cooked beef to the pan and pour the prepared sauce over the mixture.
Toss everything together for 1 minute until the sauce thickens into a glossy glaze that coats the beef and broccoli.
Remove from the heat, drizzle with toasted sesame oil, and garnish with sesame seeds before serving.