Slice the flank steak against the grain into thin strips and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, minced ginger, minced garlic, and arrowroot starch 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 in a single layer and sear for 2 minutes until browned, then remove from the pan and set aside.
Add the broccoli florets and a splash of water to the pan, covering for 2 minutes to steam until vibrant green and tender-crisp.
Return the beef to the pan, pour in the sauce mixture, and toss constantly for 1 minute until the sauce thickens and becomes glossy.
Remove from heat, drizzle with sesame oil, and garnish with sesame seeds before serving.