Remove the turkey neck and giblets from the turkey cavity and place them in a small saucepan. (The giblets include the gizzard, heart, and liver, and the neck.)
Cover with broth and bring to a boil for 5 minutes.
Reduce the heat to low and simmer for 2 hours (while the turkey is cooking).
In the same roasting pan used to cook the turkey, sprinkle in the flour and whisk until the mixture becomes a paste, also known as a roux.
Remove and discard the turkey neck and giblets from broth.
Slowly stir in the broth in the roux while whisking the whole time.
Whisk and cook the roux over medium-low heat until deep golden brown.
Add pepper. Allow to cook for several minutes, whisking occasionally.
When the gravy is well mixed and has thickened to the consistency you like, pour into a gravy bowl.
The paste you make is called a roux. It is a mixture of fat and flour to make gravy. If the paste is too thick, add a little more grease (olive oil). If it is too greasy, sprinkle in more flour.