Start by taking out all of the accumulated containers from the freezer.
Empty them into your stock pot. (The one I used is a 2 gallon pot. I have a larger one, but I don't need that much stock, plus it's useful to have a larger pot for the later straining step.)
You might notice that I have some scraps of red cabbage in the pot. Didn't think about the fact that it was going to make my stock turn purplish.
Cover with water.
Bring to a boil, then reduce to a simmer. Simmer, covered with the lid slightly open, for about an hour.
Notice the slightly purple color, due to the red cabbage. It's okay, though, as the stock still tastes good. If you care about the color, avoid things like red cabbage and beets.
After turning off the burner, I usually let it cool for a while uncovered, as it makes the next step a bit easier. Get another pot, of equal (or larger) size, and put a strainer on the top. Pour the stock through the strainer.
(You can tell it's an action shot, because it's blurry.)
I usually leave it to sit for a few minutes to let everything drain off. This is when having a larger pot can be helpful, as the strainer will be completely out of the stock. If the strainer is sitting in the stock, you'll need to lift it up and hold it to finish the draining.
Pour your stock into containers. I like to use quart-sized Mason jars, as they hold 4 cups, which is the right amount of stock to make risotto with a cup of arborio rice. I also use a larger glass jar that I have, from which I'll pour off what I need.
Definitely a red/purple hue to this batch....
You could also freeze the stock, in one, two, or four cup measures. With the winter and my overrun of root veggies, I've been making lots of soup, so I'm going through the stock in a week or less. With that rate of use, I just leave it in the fridge.