I got this recipe from Amy Matassa who got it from Sheryl Rosedoff Bergman
Balsamic Roast Beef Recipe
1 3-4 pound boneless roast beef (chuck or round roast)
1 cup beef broth
1/2 cup balsamic vinegar
1 tablespoon Worcestershire sauce
1 tablespoon soy sauce or coconut aminos
1 tablespoon honey
1/2 teaspoon red pepper flakes
4 cloves garlic chopped
Place roast beef into the insert of your slow cooker. In a 2-cup measuring cup, mix together all remaining ingredients. Pour over roast beef and set the timer for your slow cooker. (4 hours on High or 6-8 hours on Low)
Once roast beef has cooked, remove from slow cooker with tongs into a serving dish. Break apart lightly with two forks and then ladle about 1/4 - 1/2 cup of gravy over roast beef.
Store remaining gravy in an airtight container in the refrigerator for another use.
If you prefer a more pronounced flavor, once the roast beef has been removed, use a fat separator on the gravy and then pour the gravy into a saucepan over medium heat. Simmer until the gravy has reduced by half.