Genetics. You simply reverse engineer the previously designed product and then determine what genetic codes and information you need to design the new organism in the way you want.
Seems to me that the geneticists are using the "creation model" in creating new orgainsims. They certainly aren't changing the environment and then waiting for the changes to occur on an evolutionary level. They are actively involved in "intellgently designing" new organisms.
Why not just build the new organism in the first place?