Preheat a deep skillet over high heat. Brown the beef cubes on all sides. Remove the meat from the skillet and place it into the slow cooker.
In the same skillet, sauté the carrots and onion and cook until they are lightly browned. Place them into the slow cooker.
Next, brown mushrooms in the same skillet and add to the slow cooker.
Add barley, bay leaves, Better than Bouillon broth concentrate, and salt to the slow cooker. Fill the slow cooker with enough water to cover 2/3rds of the ingredients (about 2.5 cups).
Depending on the size and power of your slow cooker, cook on high for 2-4 hours. Check the stew periodically to gauge doneness. Serve hot and enjoy!