In a small bowl, whisk together the tamari, raw honey, grated fresh ginger, minced garlic, arrowroot powder, and water until the powder is fully dissolved.
Slice the flank steak against the grain into thin, bite-sized strips to ensure maximum tenderness.
Heat the toasted sesame oil in a large wok or cast-iron skillet over medium-high heat until it begins to shimmer.
Add the beef strips in a single layer and sear for approximately 2 minutes until deeply browned, then remove the beef from the pan and set it aside.
Add the broccoli florets and sliced red bell pepper to the same pan with a small splash of water, then cover with a lid for 2 minutes to steam-soften the vegetables.
Remove the lid and return the beef to the pan, pouring the prepared sauce over the mixture while tossing constantly.
Continue to stir-fry for 1 minute until the glaze becomes thick, glossy, and coats every ingredient.
Garnish the dish with sesame seeds and red pepper flakes before serving immediately.