Slice the flank steak against the grain into thin, bite-sized strips and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, toasted sesame oil, minced garlic, and grated fresh ginger to create the stir-fry sauce.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the steak 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 splash of water, covering with a lid for 2 minutes to steam until they are bright green and tender-crisp.
Return the beef to the pan, pour the sauce over the mixture, and toss everything together for 1 minute until the sauce thickens and coats the ingredients.
Garnish with sesame seeds before serving.