The Baby Doll here is tied on a longshank hook which is my personal preference. They can be tied on Kamasan B175 or Hayabusa 761 hooks and be just as effective.
STEP 1 : Catch in the thread towards the bend of the hook. (Varnish it if required and leave to dry).
STEP 2 : Take a length of around 13" of wool and untwist it so that you have the strands as pictured. Wool varies and can have anything from two to five strands twisted together to make up one length of wool. Catch in two or three untwisted lengths at the hook bend as shown.
STEP 3 : Return the thread to the eye. Now build up a body by winding the wool strands back and forth along the hookshank. Make sure that you finish at the eye and have around 2 inches of length left over. Do not trim this length.
STEP 4 : Holding the excess length taught with the left hand, create a neat head using the thread, whip finish and cut away thread. (AGAIN - Do not trim the excess length of wool).
STEP 5 : Catch in the thread again where we first started. Pull the excess wool backwards and make sure that it lies flat and tight along the top of the body. Secure with thread, whip finish and cut away the thread. Pull the lengths of wool together that are now acting as the tail and trim to length.
STEP 6 : The resulting fly.
If you need to add a different colour back, then before you wind the wool (Step 3). Catch in two strands of untwisted coloured wool and leave its length over the eye. Then create the body as usual and the rest of the procedure is the same. Here's a white baby doll with a Green Back.