In a large pot, add chicken backs and chicken drumsticks.
Add enough water to cover all of the meat. Set over high heat, cover, and bring to a boil. As soon as it starts boiling, remove from heat and drain off the water. Rinse the meat, refill with fresh water (enough water to cover all of the meat, plus an extra 1 cm over the meat). Don't add too much water or it won't be "gelatiney" enough later. Cover and bring to a boil again. Reduce heat to a light boil/simmer and set a timer for 5 hours.
After cooking for 5 hours, add 1 large carrot, 2 medium onions (both ends removed), 1 celery stick, 2 bay leaves, 5-8 peppercorns, and 2 tsp salt into the pot then continue boiling on low heat for 1 more hour. It should look like a nice chicken broth. Now it's important that you do not discard the broth and do not add more water to the pot!
Remove the drumsticks and carrot from the broth and let them cool. Discard chicken backs, onion, and bay leaves.
Use a fine mesh sieve with 3 bounty paper towels over the sieve and filter the broth through the paper towels. You will be left with a clean broth.
Peel and press 4 garlic cloves into the broth and do a taste test to see if more salt is needed.
Once the meat has cooled, use a fork to separate meat from the bones. Keep the good meat; discard the bones. Thinly slice the carrot. You can make one big kholodets in a rectangular pyrex dish or you can make smaller serving bowls.
Start by placing carrots on the bottom then top with some dill if you wish. Next, add the meat in an even layer and pour broth over the meat; enough to cover the meat and a little extra over the top. Refrigerate 3 hours or overnight, or until firm.
Serve with red horseradish or Russian mustard. Once it's set, set the bowl in hot water for a few seconds, then use a slim spatula to release the gelatin from the dish. Or you can just serve it out of the dish and save yourself a step.
Offer a section of a lemon to sprinkle with to enhance the taste.