Step 1

Place roast beef in a lightly greased slow cooker.

Step 2

In a small bowl, combine beef broth, 1/3 cup balsamic vinegar, 2 tablespoons soy sauce, honey, red pepper flakes, garlic and pepper. Pour over roast beef.

Step 3

Cover and cook on low for 6-8 hours or until beef is tender.

Step 4

Remove roast from slow cooker and slice or shred. Cover and keep warm.

Step 5

Remove 1 1/2 cups of liquid from the slow cooker and pour through a mesh strainer into a medium saucepan.

Step 6

Stir together cornstarch and water in a small bowl. Whisk into saucepan, along with 3-4 tablespoons balsamic vinegar, brown sugar and 1 tablespoon soy sauce.

Step 7

Bring to a boil, whisking constantly, until mixture thickens. Season with salt and pepper, to taste. If desired, add additional water or cooking liquid for a thinner glaze.

Step 8

Pour glaze over beef and serve.