Repeat with your secondary fabric, if using one.
Now with what will be your skirt laying straight, pin the ruffles on where you'd like them to lay. Don't be afraid of twists and turns, they can be a much prettier finished product than if your ruffles were to just lay straight. Weave the ruffles through each other at a few points for added interest and stability.
Now let's sew them on! Simply sew a straight stitch (with tighter tension than your gathering stitch) up the center of each ruffle. Your seams don't need to be dead on the center- on a skirt like this imperfection adds character- but make sure every ruffle is sewn completely on from one end to the other!
At this point the lovely recipient of the skirt will be hanging by your elbow, simply dying to try it on. No fear, you're almost done. Take the top of the skirt and fold it over twice, sewing in place while leaving a large enough tube to slide your elastic through. Make sure you leave a couple of inches unsewn to insert the elastic!