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, arrowroot powder, 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 beef strips in a single layer and sear for 2 minutes per side until browned and tender, 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 bright green and crisp-tender.
Return the beef to the pan, pour the sauce over the mixture, and toss constantly for 1 minute until the glaze thickens and coats everything evenly.
Garnish with sesame seeds and serve immediately while hot.