Slice the flank steak against the grain into thin, bite-sized strips.
In a small bowl, whisk together the rice vinegar, tamari, honey, and ground ginger to create the tangy glaze.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Season the beef strips with sea salt and black pepper, then add them to the hot skillet.
Sear the beef for 2-3 minutes until browned, then remove the beef from the pan and set aside.
Add the broccoli florets and minced garlic to the same skillet with a splash of water, covering for 2 minutes to steam-soften.
Return the beef to the skillet and pour the prepared tangy glaze over the mixture.
Toss everything together for 1-2 minutes until the sauce thickens and coats the beef and broccoli.
Serve the stir-fry immediately over the warm cooked brown rice.