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, minced ginger, minced garlic, and arrowroot powder to create the stir-fry sauce.
Heat the toasted sesame 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, then remove the beef from the pan and set aside.
Add the broccoli florets to the same pan with a splash of water, cover with a lid, and steam for 3 minutes until tender-crisp.
Return the beef to the pan and pour the sauce over the mixture, tossing constantly for 1 minute until the glaze thickens and coats everything evenly.
Garnish with sesame seeds and serve immediately.