In creating a flower girl, or beauty pageant dress, you create a very large bow that hangs down the back like a bustle. The bow can include flowers, and can be tied separately from the waist sash, or as part of it.
For a wedding dress, the bustle sash can be gathered up as part of the train, or in a separate bustle, tied or pinned on top.
There are many excellent pictures of bustle sashes on the internet which you can see by typing “bustle sash” in your “image” search box. On the bustle sash search list I have provided (see links on the left side of your screen) you will find many sources of information depending on the type of clothing you are accessorizing (flower girl, wedding, kimono, etc.)
For a very good illustrated wedding bustle “how to” don’t miss www.leanna.com/Bridal/Bustles.htm