If the broth and giblets were prepared in advance, bring them to room temperature before making the gravy. If you’re using a brined turkey, please taste the gravy before adding any additional salt.
Remove cooked turkey and rack from the roasting pan. Pour the turkey drippings into a medium-sized bowl or a 4-cup measuring or gravy skimmer cup. Let the mixture settle, allowing the fat to rise and separate. Skim off 1/3 cup fat from drippings and pour into a 2-quart saucepan. Set aside. Skim and discard remaining fat from drippings.
Deglaze the turkey pan: Place pan on 2 burners, pour in 1 cup of Turkey Giblet Broth, and cook over medium heat, gently loosening and scraping all the crusty, browned bits at bottom of the pan. When liquid starts to simmer, remove from heat and pour mixture into the skimmed turkey drippings. Add enough turkey broth to the bowl with the turkey drippings to equal 3 cups total.
Add flour to saucepan with fat. Over medium heat, whisk mixture until very smooth and a light golden color, about 3 to 4 minutes. Slowly pour 1 cup of the turkey broth/drippings mixture into pan, whisking until thoroughly combined. Add 2 more cups of broth to pan, continue cooking and stirring for several minutes, until the gravy simmers around edges of the pan, begins to thicken and coats the back of a spoon. Stir reserved chopped neck and giblets into gravy and heat an additional minute or two. If gravy is too thick, add more liquid to achieve desired consistency. Season to taste, pour into gravy boat and serve immediately. Gravy will thicken as it cools.