I keep the bones, carcasses, and other bits and pieces left over from meals and freeze them in ziplocs. I'll also toss in the gelatinous goo and other drippings

I keep the bones, carcasses, and other bits and pieces left over from meals and freeze them in ziplocs. I'll also toss in the gelatinous goo and other drippings from roasting whole birds, wings, or thighs. (Sometimes this is ~1/2 the volume of the resulting stock). When there's enough, or I'm running out of space in the freezer, I plop all of that into a 8 or 12 qt stockpot, with a couple carrots, an onion and a couple stalks of celery. Enough water to be mostly full. (If it's hard to fit the frozen bits, pour near-boiling water from a kettle over it to fill the pot). Bring to a boil, back off to a light simmer, let it go for a few hours. Skim off the bulk of the fat, (reserve or not, I had 1/2 L for 3.5L of stock yesterday) Pour it out through a colander into a large bowl to strain the chunks, skim most of the fat out and put it in quart jars for freezing. If stored in the fridge, it's basically solid. If you need more meaty bits, roast some wings. They've got the best mix of meat and collagen for stock. I just toss all the solids, the meat is mostly tasteless at that point, though the dog likes the carrots. (and occasional bits of the meat)