That line about a gallon bag going back to March got me because I did the same thing with veggie scraps and didn't start until my sister nagged me about it. What worked for me was keeping a bag in the freezer door and just tossing in onion skins, carrot peels, and celery ends as I cooked, no extra steps at all. When the bag fills up I dump it in a pot with water and let it simmer a couple hours, then strain it and freeze the stock in old yogurt containers. The one thing I learned the hard way is to skip broccoli and cabbage scraps because they make the whole pot taste bitter. Also don't let the bag sit too long or the freezer smell gets weird. It's honestly the easiest way to get free stock out of stuff you were already throwing away.