I made a set of flashes to go with the last kilt I made. It wasn't as hard as I'd expected.

I cut a strip a little over twice as wide as I wanted each individual strip to be - with the desired stripe centered - folded them in half, and sewed it together along the long open side. Turned it inside out (sew that the stitching would be inside) centered the stripe, and pressed.

After pressing, I folded the top over the appropriate amount, and sewed it down to form the loop. I then cut the upside down v-shape out of the bottom and slid them onto the velcro. They're working great for me, but I'm trying to decide what I would do slightly different next time.