I'd start making pants that LOOK like they're low-slung and show off the unmentionables, but actually DON'T.
It should be fairly simple for anyone with any proficiency on a sewing machine.
Just cut off the top of a pair of drawers and sew them onto the top of a pair of jeans. They then become one article of clothing that simulates the look that literally has the Fashion Police in an uproar.
And it'd make me quite a bit of coin, I'd guess.