This is very easy to make, and it's delicious. We save up all of our vegetable trimmimgs by putting them in 1-gallon freezer bags and freezing them until we have 4 or 5 bags full. Then we put them all in a big pot. Add just enough water to cover ... this will be hard to get right because all the veggy trimmings will be frozen, and they'll settle down a lot once they heat up. It's best to start out with too little water and add some later. Bring it to a boil then quickly turn it down to a simmer. Let it simmer for a couple hours, then pour through a strainer into another pot and transfer to jars. Let cool, then refrigerate. You can pressure can it if you like. Almost anything is good for adding to the stock except you want to avoid cabbage and other cole crops like broccoli, collards, etc. They don't do too well. Trimmings from potatoes, corn cobs, green beans, onions, mushroom stems, parsley, etc. are all great. I usually add a tablespoon of wholepeppercorns to the boil.