Remove 1 1/2 cups of beef drippings/juices from the crockpot. If you don’t have enough, you can add beef bullion broth until you get to 1 1/2 cups. Pour the beef drippings/liquid into a saucepan. In a small bowl, mix together 1/4 cup of cold water and two tablespoons of cornstarch until smooth. Whisk the cornstarch mixture into the saucepan. Bring the gravy to a boil over medium heat, stirring constantly, and boil for 30-60 seconds until thickened.