It takes me about two days to make stock from a cooked carcass.
I pack the bones in tightly, add whatever else, press it down, and only add
enough water to cover the bones.
I put in veggies, maybe lemon rinds, almost always some garlic, bay leaf...I wait to add salt until I use the stock: in case something spoils, it can be composted.
I get it up to a good boil, and simmer it a while, usually the time it takes to make dinner. Then I let it cool on the stove, being careful not to disturb the lid and introduce bacteria. Every 8 hours or so, when I remember, I simmer it some more.
On the second or third day, I empty the stock and replace the water, and start again. Even the second go-round usually gels like you show.
I recently forgot one such pan of stock for about a week. It didn't smell or look spoiled as I put it on the
compost pile, but I didn't want to risk it.
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.