Add the turkey carcass and scraps to the slow cooker. Also add in the chicken feet, if using.
Pour white vermouth into the slow cooker.
Add all remaining ingredients to the slow cooker, and fill with enough water to cover all the ingredients, but take care to leave at least a one-inch headspace in the slow cooker. Do not fill the slow cooker to the rim. If some of the ingredients are popping over the top of the water, that is okay. They will shrink and sink during the simmering time.
Set the slow cooker to high for one hour, then turn down to "keep warm". Allow the bone broth to simmer on keep warm for six hours. If your slow cooker does not have a keep warm setting, turn it down to low. If, during the simmering process, the bone broth boils, tilt the lid of the slow cooker to release the heat. You want to see only periodic bubbles as the bone broth simmers. If you have a food thermometer, you can check the temperature of the bone broth. It should simmer at 180°F. But if you do not have a food thermometer, just watch the bone broth and make sure that it stays at a low simmer with only periodic bubbles.
After the six-hour simmer on keep warm, remove all the solids.
Once the solids are removed, strain the bone broth through a flour sack towel or cheesecloth to remove any remaining bits of debris.
At this point, you may decant the bone broth or use a fat separator device to remove the fat and then decant it.
The bone broth will be at its freshest for 2-3 days, refrigerated. If you keep a substantial fat layer on top of the broth, it may stay fresh for 1-2 weeks, refrigerated. If frozen, the bone broth will be at its freshest for 2-3 months but may retain its freshness up to 6 months.
To drink as a beverage, reheat gently and add sea salt to taste, if needed. For recipes calling for water such as soups, stews, or the cooking of grains, use bone broth in place of the water.