Hey gang this morning I started boiling about a pound and a half of chicken bones in a 2 gallon stock pot, I reduced it down to about a quart and I stuck in the fridge to skim off the top but it has turned into jello.
Quite normal. It means you have a good amount of gelatin from the bones in there which has set to a jelly stage. Not a problem. This is how I expect mine to be. Skim off the fat cap and you will have a lovely stock underneath. You may have reduced it a bit too far, but that is easily resolved by adding just some plain water when you plan to use it.
Chook necks are good too, I like wings as well. So much bone vs meat. If you are after a "white stock", don't brown off your bones or veg first, and only use celery and onion. If you after a "brown stock", roast off veg, celery, carrots, bones until caramelised. After that it is pretty much the same process. It can help to skim the stock before adding the veg, as this will help keep it clearer.