There is a good article with instructions for making these types of clear bags in the October 2007 edition of Sea Kayaker magazine (written by Bryan Hansel, who posts here).

kelly t

: Has anyone tried building and using Tom Yost style dry bags? Just stumbled on
: this and really appeals to me.

: Tom, I know you post on here. Would love to know more about building these. I
: don't have any drybags and am going to need several for our camping this
: summer. If this work well ad hold up, looks perfect for me!