Thank you everyone for the input. I will try to answer all in order.
@Frisk DreemurrThank you, I will give this a go as soon as I come across one and revert back.
@ifozThank you, when looking at the recipes it almost seems as if some of the old content is still there that needs to be removed. When clicking on the item there is no "obtained by" section.
@dakkoThank you, I also believe this should be possible with the pelt, but the recipe for the mantle requires the raw hide (not oiled/cured to become a pelt).
@VenusgateI am unable to get the head removed from the hide with any knife (that I have access to) unfortunately, which is the part I do not understand. I tried copper shears as well. If you have any advice regarding this, please let me know. You are correct in that you can throw it into a barrel with limewater to get the prepared headless hide. I have made a lot of leather this way, but only noticed after the fact that leather isn't used to keep you warm. Thank you for the reply.