Flipping over to the right side of the fabric, pin the lace edging all around the bottom and curved edges of the 3 ruffles + the little 2" long piece (over your ironed hem). Its easier to do this now before you ruffle your fabric. Don't attach the lace to your full base skirt, unless you want to keep it its full length. I wanted mine shorter in front, but I didn't know how to cut that shape until I had it put all together. So I waited to cut & lace that piece.
Then, individually, fold each of the raw edges under & press (diagram).
Ok, now you've got your waistband + interfacing & your little 2" long piece + all your ruffles!! Next you want to lay it all out to line it all up and make sure your ruffles are distributed the way you want. Be sure that the edges of your full base skirt line up perfectly with the edges of the waistband and the edges of the little 2" piece. Next make sure your 3 ruffle layers line up the way you want. I wanted them to get progressively narrower as they went up (see photo). You can move them around (tighten/loosen) anyway you like.
Next, pin the whole kitten caboodle together. I did this in stages so I could make sure I did it right. I pinned all the ruffles together + full base skirt. Then I pinned the little 2" piece on top.
Then I opened up the waistband and flipped it over (photo) and pinned the inner part of the waistband to the rest of the layers. This is A LOT of layers of fabric. I then sewed the whole lot along the line I drew in the interfacing to secure everything together. This is the stitch that is keeping your whole skirt together, so you might want to go over it twice. Make sure you've done a good job pinning so that you catch all the layers in your sewing.