I would look through the pattern companies web sites for a strapless bubble skirt dress. it'll be there somewhere.
Once you have the pattern, copy the bodice pattern pieces onto some other paper. now you can draw that jagged top without accidentally exposing yourself. Put away the original pattern pieces and use your copied amended ones when cutting your dress out.
when sewing, obviously you'll be doing the top edge differently, possibly putting boning in the jagged bits so they stay up. But essentially, it'll be the same process as instructed, just different shapes resulting. Good luck!