I like to place sliced onion and granny smith apple under the turkey when roasting. When I use the stock from the turkey for gravy it has a sweet savory flavor.
I roast sliced onions and shallots along with the turkey. I skim the fat and puree the drippings along with the onions and shallots and some stock made from the giblets and neck and the chopped giblets and neck meat. It makes a wonderfully tasty gravy without having to use flour or corn starch and worry about it being “gloopy”.