about 1 Tablespoon flour and 1 Tablespoon cornstarch
Take roast out of the pot. Hopefully you will have 1 cup of liquid, maybe add water and beef cubes. Mix the flour and cornstarch with warm water (mix well!) and stir in slowly into liquid in the pot (make sure the liquid is boiling first). Add LOTS of salt and pepper. LOTS.
If you've ever had the gravy Bill makes, this is it.