Thinly slice the flank steak against the grain into bite-sized strips to ensure maximum tenderness.
Whisk together the coconut aminos, arrowroot powder, and toasted sesame oil in a small bowl until the powder is fully dissolved.
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, seasoning with sea salt and black pepper, and sear until a brown crust forms, about 2 minutes per side.
Remove the beef from the pan and set aside; add the broccoli florets with a tablespoon of water, covering with a lid for 2 minutes to steam.
Stir in the minced garlic and grated ginger, sautéing for 30 seconds until the aroma fills the kitchen.
Return the beef to the pan, pour the prepared sauce over the ingredients, and toss constantly until the sauce thickens into a glossy glaze.
Sprinkle with sesame seeds and serve immediately for the best texture.