Begin by slicing the lean flank steak against the grain into thin strips.

Separate the baby bok choy stems from the leaves, rinsing them thoroughly.

Mince the garlic and grate the fresh ginger, setting everything aside.

In a large skillet or wok, spray cooking spray and heat over medium-high heat until shimmering.

Add your sliced flank steak to the hot skillet in a single layer and cook for about 4-5 minutes.

Return the skillet to the heat, adding the minced garlic and grated ginger, cooking for about 1 minute.

Add the separated bok choy stems and sliced red bell pepper, stir-fry for 3-4 minutes.

While the vegetables are cooking, whisk together the low-sodium soy sauce, rice vinegar, sesame oil, cornstarch, and water.

Pour the prepared sauce over the stir-fried veggies and beef, stir together and cook for an additional 1-2 minutes.

Remove from heat and transfer to a serving dish. Garnish with sliced green onions and sesame seeds.