Step 1: Prepare the Marinade

In a medium-sized bowl, whisk together the low-sodium soy sauce, beef broth, honey, balsamic vinegar, minced garlic, Worcestershire sauce, black pepper, and red pepper flakes. Mix until the honey is fully dissolved and all the ingredients are well combined. This aromatic mixture is the heart and soul of the recipe.

Step 2: Sear the Flank Steak (Highly Recommended)

Pat the flank steak dry with paper towels. A dry surface is essential for getting a good sear. Heat the olive oil in a large skillet or cast-iron pan over medium-high heat. Once the oil is shimmering, carefully place the flank steak in the pan. Sear for 2-3 minutes per side, just until a deep brown crust forms. You are not trying to cook the steak through, only to develop flavor through the Maillard reaction. This simple step creates a depth of savory, roasted flavor that you can’t achieve by simply placing the raw meat in the slow cooker.

Step 3: Combine in the Slow Cooker

Place the seared flank steak into the basin of your slow cooker. If you have any thinly sliced onions, you can create a bed for the steak to rest on. Pour the prepared marinade mixture directly over the steak, ensuring it’s mostly submerged.

Step 4: The “Low and Slow” Cook

Cover the slow cooker and set it to cook. For the most tender, fall-apart results, cook on LOW for 6-8 hours. If you’re shorter on time, you can cook on HIGH for 3-4 hours, but be aware the meat may be slightly less tender than the low-and-slow method. The goal is to gently break down the connective tissues in the meat over a long period.

Step 5: Thicken the Sauce

Once the cooking time is complete, the steak should be incredibly tender. Carefully remove the flank steak from the slow cooker and place it on a cutting board. Let it rest for a few minutes.

Meanwhile, create the perfect gravy from the remaining liquid in the slow cooker. Pour the liquid into a small saucepan and bring it to a simmer over medium heat. In a separate small bowl, whisk together the 2 tablespoons of cornstarch and 1/4 cup of cold water until it forms a smooth, lump-free paste (this is called a slurry). Slowly pour the cornstarch slurry into the simmering sauce while whisking continuously. Continue to simmer and whisk for 2-3 minutes, or until the sauce has thickened to a rich, glossy, gravy-like consistency that coats the back of a spoon.

Step 6: Shred and Serve

While the sauce is thickening, use two forks to shred the rested flank steak. It should pull apart with very little effort. You can also slice it thinly against the grain if you prefer slices over shreds. Place the shredded steak back into the now-empty slow cooker basin or into a large serving bowl. Pour the thickened, luscious sauce over the shredded meat and toss gently to coat every piece. Garnish with sliced green onions and a sprinkle of sesame seeds before serving.