I did this one using foam glued together with Super 77 spray. I use a tool that is made by a fellow that owns the Soggy Bottom fly shop, it goes in a dremel tool and I use a nail file to turn it down to the sise you want.
I used to use cork, but the foam is much easier to work with, at least to me. If I want to make them look good, I coat them with Liquid Fusion after putting any color on them.