I simply save all my bones from regular meals in a large ziplock in the freezer (rib bones, chicken bones, etc., all cooked already).

Then, when the bag is full, I pressure cook them for three hours, sometimes adding spices or garden veggies like leeks or onions (sometimes I'll even freeze leftover veggies or trimmings in the bone bag).

Once the bone broth is made I freeze it in ice cube trays and it will often last me till the next bag of bones is ready - I give my little dog one cube a day as well.

The broth comes out fantastic - flavourful and very gelatinous - despite the fact that I am a bone "gnawer" and all my bones have had every scrap of fat and grizzle completely chewed off!

I did, however, buy beef knuckles once to add to a broth and I roasted them first. I would think that raw bones would be way less tasty - resulting in a blander broth. The knuckles were so tempting after roasting that I made a meal out of chewing on them before throwing them in the pot, so it sort of makes sense, doesn't it?