Preheat your oven to 400 degrees F. Lightly grease a large baking sheet. (I used foil in the photo above out of habit, but there is no need.)
Place wings and other turkey parts on the pan. Scatter the onions over the pan.
Roast at 400 for 1 hour, up to an hour and 15 minutes. Make sure the parts are browned on top.
Remove the turkey parts to a large stock pot.
Place the baking sheet over two burners on your stove and turn both of them up to medium. Add 1 cup water and use a wooden spoon to stir up all the browned bits. When the bottom of the pan is clean, scrape the water into the pot with the turkey.
Add 6 cups chicken broth (or 6 cups water and 6 teaspoons turkey base.) Add the chopped carrots and the thyme.
Simmer uncovered for about 1 and 1/2 hours.
Remove the turkey parts and set aside. (You can pull off the meat and save it for something else, but I found that it was pretty tough.)
Pour the remaining onion and carrot mixture through a colander into a bowl. (You can discard the veggies or snack on them).
At this point I stuck the bowl in the freezer for about 20 minutes so that it was easy to skim the fat from the top.
Pour the broth back into the pot. Bring to a gentle boil.
Whisk together the flour and 2 cups broth, making sure to get out all the lumps.
Slowly whisk the flour mixture into the broth. Boil for 5 minutes, stirring. Stir in butter, pepper, and salt.
Taste it and see what you think. You can add more salt, pepper, thyme, or up to 1 teaspoon of turkey base.
Let cool and freeze in ziplock bags. Let the gravy thaw in the fridge overnight, or just stick it in the microwave.
If you are making a turkey on the day you plan to serve this gravy, add the fat-skimmed pan drippings to the gravy!