Slice the flank steak against the grain into thin strips and season with the sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, grated fresh ginger, minced garlic, and arrowroot powder to create the stir-fry sauce.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the beef strips to the pan in a single layer and sear for 2-3 minutes until browned and caramelized, then remove and set aside.
Add the broccoli florets and a splash of water to the same pan, covering with a lid for 2 minutes to steam until tender-crisp.
Return the beef to the pan and pour the sauce over the mixture, tossing constantly for 1 minute until the glaze thickens and coats everything.
Remove from heat, drizzle with toasted sesame oil, and garnish with sesame seeds before serving.