If you have access to any full-flavored stock or broth, you can easily make gravy. Canned broth works fine, but homemade stocks will make a much better gravy. There are several methods of thickening the gravy, and my favorite involves making a roux (equal parts of flour and butter or oil).

You simply cook the flour and oil/butter in a heavy saucepan or skillet, stirring constantly, until the color desired. (If you want a blond gravy, such as for chicken, only cook until a blond color. If you want a dark, rich gravy for red meat, cook the roux until milk chocolate brown. Add some chopped onions, celery, bell peppers, garlic (any flavors you like), and cook the vegetables in the roux until they are soft.

Whisk in the stock, and bring gravy to a low simmer. Cook until thickened and the flavors have come together. Add any extras you may like, such as chopped green onions, fresh herbs, or other spices and seasonings. For every 2 cups of broth or stock, you will need about 2 tablespoons of flour to thicken. Of course, if you like a thinner gravy, simply use less.

An even simpler method involves using cornstarch. Simply mix a little cornstarch with just enough cold water to form a pourable "slurry," then add this slurry, little by little, to hot stock or broth. As the stock comes to the boil, the cornstarch will work to thicken the sauce. You can always add more slurry if your gravy isn't thick enough, but always wait until the sauce boils between additions, to make sure you really need more.