Combine the spices, then rub them over the chicken.
Throw the onion into a slow-cooker, top with the chicken, and cook on low for 2 hours.
Remove the meat from the bones and cartilage, then toss the bones and cartilage back into the pot with any vegetables you may need to get rid of or vegetable refuse like onion skins, carrot ends, green leeks, etc. (this technically turns our broth (which is just bones) into a stock (which has veggies and/or meat), but whatevs), and enough water to cover 2" over the top. Cook on high for about ten minutes.
Pour out all the water. This discards all the "scum" that has already cooked off of the bones. Refill the pot with fresh water and add a splash of apple cider vinegar. Cook another 24-48 hours on low. (Meanwhile, eat the meat!)
Strain the liquid into a jar, preferably into single-serving jars so that you can freeze the ones you won't be using in the next few days. A good-quality broth will gel in the fridge, and liquefy upon re-heat. Skim the fat off the top and discard it (poultry fat is high in omega-6s even when it is pastured, so I don't use it) before using your broth however you like!