Thinly slice the flank steak against the grain into bite-sized strips and season with the sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, toasted sesame oil, grated fresh ginger, and minced garlic to create the stir-fry sauce.
Heat the avocado oil in a large skillet or wok over high heat until it begins to shimmer.
Add the beef strips to the skillet in a single layer and sear for approximately 2 minutes until well-browned, then remove the beef and set it aside.
Add the broccoli florets to the same skillet with a tablespoon of water, then cover with a lid for 2 minutes to steam-fry until tender-crisp and bright green.
Return the beef to the skillet, pour the prepared sauce over the mixture, and toss for 1 minute until everything is well-coated and the sauce has thickened.
Plate the stir-fry immediately and garnish with a sprinkle of sesame seeds.