Pick a couple of fun fabrics in coordinating colors - you need the length to be about 1 yard for adult headbands.
Make a snip about 1 - 2 inches wide, and TEAR your fabric. It is amazing how cool this ends up looking, and how it comes out in a straight line! If your first tear is not straight compared to your edge, make another snip and tear again. The grain will stay the same, but may not be in line with the manufactured/cut original edge.
Lay them on top of eachother, so the wider one is on bottom. If you want to taper your ends slightly, do that now with scissors.
I will show you how I made the ones in the pictures here.
Tear a piece of fabric about 1" wide and 1 foot long.
Tuck the end under and start to twirl the fabric in a circle.
I twist and twist my headband, sewing the circle tighter and tighter, catching the layers of the twirly flower as I go. Do this with 3 or 4 flowers, overlapping each flower a bit if you want, sewing each individually. It ends up looking like this: