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 garlic, grated ginger, arrowroot powder, and water to create the stir-fry sauce.
Heat the toasted sesame oil in a large skillet or wok over 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 to the same pan with a splash of water, cover, and steam for 3 minutes until vibrant green and tender-crisp.
Return the beef to the pan, pour the sauce over the mixture, and toss constantly for 1 minute until the sauce thickens and glazes the ingredients.
Garnish with sesame seeds before serving.