In a medium bowl, combine the flank steak, low-sodium soy sauce, cornstarch, sesame oil, and baking soda. Let it marinate for at least 10 minutes.

In a separate bowl, whisk together the beef broth, low-sodium soy sauce, oyster sauce, rice vinegar, brown sugar, grated ginger, minced garlic, and cornstarch.

Heat olive oil in a skillet over medium-high heat. Add broccoli florets and water; cover and steam for 2-3 minutes.

Increase heat to high and add the marinated beef. Cook for 1-2 minutes per side until browned and cooked through.

Reduce heat to medium-low, pour in the sauce mixture, and whisk continuously until thickened, about 1-2 minutes.

Return cooked beef and steamed broccoli to the pan, stirring to coat them with the sauce.