Bring a quart of water to a boil and add the turkey pieces, giblets, onion, celery, parsley, and carrot. Put the thyme, marjoram, peppercorns, and bay leaf into an herb infuser or cheesecloth pouch and add to the pot. Keep at a simmer boil for about an hour.
Strain the stock, and return to a simmer. Reduce to about two cups of liquid.
After removing the turkey from the roasting pan, pour the drippings into a gravy separator or small bowl and let stand to allow the fat to rise to the top. Meanwhile, add a little water to the pan and scrape up the browned bits on the inside bottom. Add this to the drippings. Remove all the fat you can from the drippings.
Make a light brown roux with the butter and flour.
Combine the stock, the defatted drippings and the roux in a saucepan over low heat. Whisk as it comes to a boil to get a smooth texture. Add Worcestershire, lemon juice, salt and pepper to taste.