In a medium-sized pot, combine the turkey neck, chopped onion, carrot, celery, and garlic. If you're using fresh herbs, add them now. Cover the mixture with water or broth.

Bring the mixture to a boil over high heat. Once boiling, reduce the heat to low, and let it simmer for about 1 to 1.5 hours. You want to extract as much flavor as possible from the turkey neck.

Remove the turkey neck and eat the meat if desired. Strain the broth through a fine-mesh sieve into a bowl or another pot, discarding the solids. This gives you a flavorful turkey stock.

Melt the butter over medium heat in a small pot. Once melted, sprinkle in the flour while whisking continuously. This mixture of butter and flour is called a roux. Cook the roux, while stirring, for about 2 minutes until it takes on a light tan color. This will help remove the raw flour taste. Slowly pour the strained turkey stock into the pot with the roux, whisking constantly to avoid lumps from forming.

Increase the heat to bring the mixture to a boil, then reduce the heat to maintain a gentle simmer. Continue to simmer, stirring often, until the gravy thickens to your desired consistency. This usually takes about 5-10 minutes.

Season with salt and pepper to taste. If you find the flavor lacking depth, you can add a splash of soy sauce or Worcestershire sauce to enhance the savory taste. Remove it from the heat once the gravy reaches your desired consistency and flavor. Serve warm over mashed potatoes, turkey, stuffing, or any other dish you like!