My turkey this year was too big to fit the entire thing into my largest stock pot, so I cut it into pieces and did two batches. Upon putting the carcass(es) in the pot (again this goes for any feathered fowl), add enough cold water so it covers the contents. Place the pot on the stove and slowly let it come to a gentle simmer -- *NOT* a boil. As it bubbles, a foamy substance will rise to the surface. With a spoon, carefully skim it off and discard the scum. Those are the impurities (blood, fat, etc.) in the bird that you do not want in your stock, that will make it cloudy instead of clear. Do not stir, just slowly skim. This may take a while and a little patience, but stay strong!
Once the abundance of foaminess subsides, add your aromatics. My preferred mix, generally speaking, is onion, carrots, celery, garlic, parsley, additional herbs (thyme, sage, oregano, chervil, rosemary ... really anything), bay leaves (like 2 max), cloves (maybe like 10), peppercorns (maybe like 10), mushroom remnants work well if I have them, ginger.... Again, it's not a recipe; it's leftover stuff in my fridge. Also keep in mind that stock is a base for a dish you will use it in, so don't worry about seasoning it or adding too many flavors; keep it simple.
After that, just keep the stock at a very low simmer, skimming the scum as needed. Let it go for 6-8 hours, replenishing the liquid as needed. Honestly, it just sits there filling your home with a potpourri of homemade wonder. My Thanksgiving turkey this year alone produced two perfect gallons of stock, which I transferred to 2-cup containers that are stored in my freezer. While the cooking time may seem trepidatious, trust me when I say it is worth the effort. It just sits on the stove while you watch TV.
Following it's stint on the stove, you will need to strain it. I use a kitchen accessory called a chinois so I can press the solids through it in order to extract the juices. However, you can use a regular strainer, lined with a couple layers of cheesecloth if you want. If you use a strainer NOT lined with cheesecloth, do not press the solids because you do not want chunks in your stock.
Ideally, one would want to put the vessel used to strain the liquid into, into an ice water bath so it cools quickly. When I do this at home, I wait for the stock to cool a little and then divide it into smaller containers (2-cup is my preference). Once it stops steaming, I put lids on and, labeled and dated, it goes in the freezer to be thawed as needed.
Additionally, it can be stored in the fridge if used within 5 days. However, one may notice that when taken out, it will look like jello. This is a good thing! When the bones cook for that long, the gelatin breaks down and releases itself into the liquid. That is a a good sign. When heated, it will melt and become liquid again. Think of it as "bone butter".
In conclusion, there are so many benefits to making stock at home. First, it saves money. I have 2 gallons of stock from one turkey for basically free. How much does a good quality stock cost at the store? I'm not talking about the bargain brand ones, with the laundry list of mystery ingredients -- the good ones. Maybe $4.00 a quart? Secondly, there's no packaging waste. Lastly, ingredients that may simply have been discarded are being utilized for another purpose. Save the carcass and enjoy!