Hi Starflux. The piece you're looking to make is called a waist cincher. While they do make them with boning and laces like a real corset, some are just decorative. You may even be able to buy one, since from a quick google search I saw a few blue ones with that diamond shape. If you want to make it, search for a waist cincher pattern or how-to. Velcro may work, but it depends on how tight you want it to wrap around you. The waist bends a LOT over the course of a day and it may tear the adhesive on velcro right off. You could try sewing the velcro on, using eye and hook closures (lots of them), or adding grommits and lacing.
EDIT: There's a post right below yours on the forum with a similar question. I was wrong, you might want to look for an underbust corset instead of a waist cincher.
Last edited by Zil : 04-29-2013 at 12:04 PM.