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, sesame oil, minced garlic, and grated ginger to create the stir-fry sauce.
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 2-3 minutes until well-browned, then remove the beef from the pan and set aside.
Add the broccoli florets and sliced red bell pepper to the same skillet with a splash of water, covering with a lid for 2 minutes to steam until tender-crisp.
Return the beef to the pan and pour the prepared sesame-ginger sauce over the meat and vegetables.
Toss everything together for 1 minute until the sauce coats the ingredients and is heated through.
Garnish the dish with sesame seeds and serve immediately.