And don't feel like you don't have time to make this if you aren't going to be home all day. It can simmer without you there watching it as long as the heat is low enough.
I buy whole chickens and save all the bones in plastic baggies in the fridge. I separate the chicken into two baggies, cooked bones and raw bones. I also have a baggie for vegetables in the freezer. When I have a baggie or two filled up, it's time to make some broth. Cooking the bones and vegetables intensifies the flavor of the broth.
Preheat oven to 450. Roast raw chicken and vegetables for about a half hour. Place all ingredients in a stockpot or other large pot. Cover with water. Bring to a boil over high heat. Skim off any impurities that rise to the top. Let it simmer all day or overnight. Just make sure it has a lot of water in there and is at a low temperature to keep too much water from evaporating.
Strain out the solids. Cool. Divide into containers. (I use mason jars.) Chill in the refrigerator. A layer of fat will form on top. You can use it as cooking fat.
Store in the freezer for longer term storage. I can some of the jars with a pressure canner. You lose some nutrients that way, but you have the convenience of being able to pop open a can and it's still much healthier than what you can find in the store.