After posting the pics of the first one, I was asked to do a photo-tutorial while I made the next one. So, here you go. :)
Basically, it is no different than your typical diaper. Just prep a couple extra pieces before sewing the layers together. The ruffle section (I bought pre-layered and pre-gathered lace ruffles by the yard at my local fabric store), and the top printed fabric section.
Fold under the edge of your print fabric and pin in your layers together, with your ruffle below your printed fabric, so that there is enough space between the ruffle and the edge for your seam allowance plus your top-stitching.
Stitch the three layers together.
The view from the back of the top layer (PUL in this case) showing the first seam.Now do the same with the printed fabric and the main body panel at the top edge. Also leaving enough space for the seam-allowance and the top-stitching.
The view from the back.
If you'll be adding snaps, this would be the time to apply them at the front (waist and rise in this case). For PUL-outer diapers, I use a second partial layer of PUL to back my snaps.
Now the top layer is all prepared. I am doing a fleece-inner cover (could also be an AI2 shell).
Pin up your ruffle (not through the PUL to avoid more punctures... just through the printed fabric) so that you don't catch any of it when sewing your layers together.
Pin or clip your layers together before sewing or serging around the edges. Lay the fabrics face to face for a turned & top-stitched style diaper.
Sew together, leaving the opening across 3/4 of the back at the middle to invert and then for your back-elastic.
Sew your elastic casing channels.
Thread through with a safety pin and tack your leg elastics.
Sew your back elastic casing channel.
Thread through the back elastic, tack at the first side, and then sew up most of the top back edge while top-stitching around that side... up until the elastic casing opening.
Pull the elastic tight, tack, and cut.
Sew up and top-stitch the other side.
Add your wing snaps.
I also hand-stitch around the cut edges of my lace at the very end to make sure it doesn't run/fray.
Here it is on a very short-waisted doll: