Sounds like Andy has a better idea. Possibly even better is to step Andy's strips back about 1/2" and then 1/4" in from the edges cut a groove with a table saw or circular saw about 1/4" deep. That will prevent water from rolling around the edge and getting into the strips Andy is suggesting, which will help prevent premature rotting. That's what I do when I make window sills.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.