What is the best way to make a flavorful gravy using stock or broth?

To make a flavorful gravy using stock or broth, start by making a roux with equal parts fat and flour. Cook the roux until it turns a light golden color, then slowly whisk in the stock or broth. Simmer the mixture until it thickens to your desired consistency, then season with salt, pepper, and any herbs or spices you like.