First, add the chicken carcasses to either your crockpot or roaster. Fill with water and add salt. Put crockpot on low or roaster at 200 degrees for 12 hours. Usually, I do this overnight.
In the morning, pick the meat off the carcasses (use this for a meal!), put it all back into the roaster or crockpot, NOW add 4 feet per bird and some chicken necks (use what you've got here! Feel free to use more or less). Add more water and leave for 6-8 more hours at the same temperature.
If you want to add any herbs like thyme or rosemary, add them in the last hour, otherwise they may turn the broth bitter.
After the final cook, strain out the solids and use the broth. We like to add the broth to quart-sized mason jars to store in the fridge.