Slice the flank steak against the grain into thin strips and season with the 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 to the hot pan in a single layer and sear for 2-3 minutes until browned, then remove the beef 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 tender-crisp.
Return the beef to the pan, pour the sauce over the mixture, and toss constantly for 1 minute until the sauce thickens and coats everything.
Garnish with sesame seeds before serving hot.