Slice the flank steak against the grain into thin strips and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, grated ginger, minced garlic, and arrowroot powder 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 to 3 minutes until browned and caramelized, then remove from the pan and set aside.
Add the sesame oil to the same pan, then toss in the broccoli florets with a splash of water, covering for 2 minutes to steam-tenderize.
Return the beef to the pan and pour the sauce over the mixture, tossing constantly for 1 minute until the sauce thickens and coats everything.
Garnish with sesame seeds before serving hot.