Slice the flank steak very thinly against the grain into bite-sized strips and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, toasted sesame oil, 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 in a single layer and sear for 2 minutes until browned, then remove the beef from the pan and set aside.
Add the broccoli florets to the same pan with a tablespoon of water, cover with a lid, and steam for 3 minutes until bright green and tender-crisp.
Return the beef to the pan and pour the prepared sauce over the mixture.
Toss everything together for 1-2 minutes until the sauce thickens and coats the beef and broccoli beautifully.
Plate the stir-fry and garnish with sesame seeds before serving.