If the fly is not too small, I can actually tie a fly just using my hands. I hold the hook between my left index and thumb. I apply the material to the hook with my right hand and hold it there until I can grasp the material with my index and thumb. The thread is on a spool and I use the slit in the spool to keep the spool from rolling loose. The half hitch is done with my right hand. The only tool used are a pair of scissors that I have on my pen knife.

From what I have read, some of the nicest early Salmon flies were made in Ireland by women only using a pair of scissors.

I don't know if they still exist but I have seen vises that were held in the left hand. There was a finger ring to hold the vise in one hand with the small finger in the ring and this left your index finger and thumb to grasp the materials. Very much what we do with a vise that is on a stand. Even the thread does not have to be on a spool. Just using a length of thread is really all that a person needs.