This is how you shorten your jeans while keeping the original hem! A great trick to reattaching the hem will keep your jeans from looking unfinished: http://www.ehow.com/how_2305591_reattach-original-jeans-hem.html?utm_source=pinterest.com&utm_medium=referral&utm_content=inline&utm_campaign=fanpage
How to hem your jeans and keep the original hem! It will work with flares. The only difference is that you need to do a small reinforced stitch to resize the hem to the width of the pants where you'll hem. Sofie Love has a blog that demonstrates this.