Asymmetrical Dress- how to do it?

I have agreed to make a friends wedding dress (!). she really likes the asymmetrical drape of the dress linked  (I don't think I linked it properly, you may have to cut and paste) below, but I don't know how to do it! Any suggestions or links would be greatly appreciated.

http://www.beautifullymodest.com/store/wedding-dresses/princess-cut/md28

Thanks !
Renee

This link to an blogger who made a similar drape in a skirt might help:
http://sincerelyyours-kate.blogspot.com/2009/02/asymmetrical-folds-skirt-pattern-review.html