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, minced ginger, minced garlic, and arrowroot powder until the mixture is smooth and combined.
Heat the avocado oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the beef strips in a single layer and sear for 2 minutes until browned and caramelized, then remove the beef from the pan and set aside.
Add the sesame oil and broccoli florets to the same pan with a splash of water, covering for 2 minutes to steam-fry until the broccoli is vibrant green and tender-crisp.
Return the beef to the pan and pour the aminos mixture over the ingredients, tossing constantly for 1 minute until the glaze thickens and glistens.
Garnish the stir-fry with sesame seeds and serve immediately while hot.