Heat oil in a large saucepan over medium-high heat. Add turkey neck and giblets; cook 5 minutes, browning on all sides. Add water and next 7 ingredients (through bay leaf); bring to a boil. Reduce heat, and simmer until liquid is reduced to about 2 1/2 cups (about 1 hour). Strain through a colander over a bowl, reserving cooking liquid and turkey neck. Discard remaining solids. Chill cooking liquid completely. Skim fat from surface, and discard. Remove meat from neck; finely chop meat. Discard neck bone. Add neck meat to cooking liquid.
Strain the reserved turkey drippings through a colander over a shallow bowl; discard solids. Place strained drippings in freezer for 20 minutes. Skim fat from surface; discard.
Place flour in a medium saucepan; add 1/4 cup cooking liquid, stirring with a whisk until smooth. Add remaining cooking liquid, turkey drippings, salt, and pepper; bring to a boil, stirring frequently. Reduce heat; simmer 5 minutes or until slightly thickened.