I thought this was going to be a question about the fastest way in-game to get thread.
Rags take an hour to butcher for 100 thread.
Small string yields 50 thread, but I don’t know how long it takes to disassemble.
Plant Fiber seems to yield less thread for more time, but I haven’t explored it much.
Once your Survival is high enough, butchering might conceivably be consistent enough to yield sinew and generates necessary additional material, especially since you can load it into a sewing tool and then unload string out of it. I haven’t lasted long enough to know how high I need to be in order to reliably get sinew, though.