Catching up on this: the leather tarp is easy to make and its description reads as if it should act as a butchering table when deployed - but it does not. The butchering rack just ignores its presence, even if it is directly adjacent.
So for now I’m just carrying a bit of lumber in the back of my DM. Mildly inconvenient, but I only need a couple big kills a year to keep me in tallow, so its not a big deal.