Thinly slice the flank steak against the grain into bite-sized strips and season with the sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat until it begins to shimmer.
Add the beef to the skillet in a single layer, searing until deeply browned and caramelized, then remove the beef and set it aside on a plate.
In the same pan, add the broccoli florets and sliced red bell pepper with a tablespoon of water, covering for 2 minutes to steam-tenderize the vegetables.
Remove the lid and stir in the minced garlic and grated fresh ginger, sautéing for about 30 seconds until the aromatics are fragrant.
Return the beef and any accumulated juices to the pan, pouring in the coconut aminos and toasted sesame oil.
Toss everything together for 1 minute to thicken the sauce and coat the ingredients thoroughly.
Garnish with sesame seeds and serve immediately while the stir-fry is hot and glistening.