Slice the flank steak against the grain into thin, bite-sized strips.
In a small bowl, whisk together the tamari, honey, grated fresh ginger, and minced garlic to create the teriyaki sauce.
Heat the toasted sesame oil in a large skillet or wok over medium-high heat until shimmering.
Add the steak strips to the hot pan, season with sea salt and black pepper, and sear for 2-3 minutes until browned; remove the steak and set aside.
In the same pan, add the broccoli florets, sliced bell pepper, and sugar snap peas, stir-frying for 4 minutes until they are tender-crisp.
Return the steak to the pan and pour the prepared teriyaki sauce over the meat and vegetables.
Toss everything together for 1 minute until the sauce thickens and creates a glossy glaze.
Serve the stir-fry over the warm brown rice and garnish with sliced green onions and sesame seeds.