Better Than Takeout: Just 5 ingredients. Put sliced steak in the slow cooker and let the sauce do the work. It comes out sticky, sweet, and savory without the delivery fee.
Slice the flank steak: Place the flank steak on a cutting board and slice it thinly against the grain into bite-size strips, about 1/4 inch thick. This helps the meat stay tender after slow cooking.
Add steak to slow cooker: Place all of the sliced flank steak into the bottom of a 4- to 6-quart slow cooker, spreading it out as evenly as you can so the sauce can coat every piece.
Make the sauce: In a medium bowl or large measuring cup, whisk together the low-sodium soy sauce, brown sugar, beef broth (or water), and minced garlic until the sugar is mostly dissolved and everything is well combined.
Combine steak and sauce: Pour the sauce evenly over the sliced steak in the slow cooker. Use tongs or a spoon to gently toss the beef so every strip is coated in the dark, glossy mixture.
Slow cook until tender: Cover the slow cooker with the lid and cook on LOW for 3 1/2 to 4 1/2 hours, or until the beef is very tender and the sauce has thickened into a sticky, caramelized glaze clinging to the meat. Avoid lifting the lid too often so the heat and moisture stay in.
Adjust and serve: Once the beef is done, give everything a gentle stir. The sauce should be dark amber, shiny, and thick enough to coat the back of a spoon. If it’s a bit thin, leave the lid off and cook on HIGH for 15 to 20 minutes to reduce and concentrate. Taste and add a splash of water or a pinch of extra brown sugar if needed to balance the saltiness. Serve hot over rice with your favorite veggies.