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, toasted sesame oil, rice vinegar, arrowroot powder, and water to create the stir-fry sauce.
Heat the avocado oil in a large skillet or wok over high heat until shimmering.
Add the beef strips in a single layer and sear for 2 minutes until browned, then remove from the pan and set aside.
Add the broccoli florets and a splash of water to the same pan, covering with a lid for 2 minutes to steam until bright green and tender-crisp.
Stir in the minced garlic and grated ginger, sautéing for 30 seconds until fragrant.
Return the beef to the pan and pour in the sauce, tossing everything together for 1 minute until the sauce thickens and glazes the ingredients.
Garnish with sliced green onions before serving.