A feather stick is a peace of wood which has been shaved to produce the great amount of thin curls or shavings as possible.
To make them all you need to have is a good peace of dry wood, Pine, Hazel or Birch are good choices and try to avoid hard woods and a sharp nice.
If you your point of start is a log, split it in quarter to obtain a good angles that your can start to work.
Now star creating long shaving along the corners angles (using the corners you will archives better shaving than the ones you will archives if you use the plat part of the wood) as thine as possible with long strokes until the end of the stick. As you move up the stick try to make them thinner and thinner until you the last ones that you will use to take a spark to the firesteel.
During this process is normal that some shaving come lose and break down but don't throw them way they will also work in starting a fire.
This was made using some pine-wood during a wood work activity with my boyscout group
Some extra information, links and videos
Carving Classic Feather Stick Tutorial
This posts is part of the "Bushcraft Academy" collection.
1. Presentation of the "Bushcraft Academy"