My materials were some scrap black lining fabric, interfacing, some poly stuffing sheeting, and some black crinoline-weight netting I had lying around.
I started by measuring the distance across the top of my tuckus, where I wanted the pad to sit. Based on this, I drew out the following pattern on paper, and cut it out of two pieces of the black lining, with seam allowance added.
my tea cozy). I pinned the interfacing on the lining, to provide a stiffened back, and placed the batting on top of that, to give a bit of body to the pad's structure.
Left - batting pinned on top of interfacing. Right - both now sewn onto fabric base.
The next step was to sew the other piece of fabric on and then flip it inside out and hand stitch closed, to produce the pad base. I also sewed a line across the top, to leave a convenient point for the pad to bend forward.
Once that was done, I cut out three widths of netting, double the width I wanted the net pouf, and at least 3 times the length of the pad's maximum width. I used the full width I had, since it was more than 3 times as long as the base. Here they are, faintly showing up on my floor, cut out.
Once gathering stitching was done, I gathered all three tubes of netting.
Left - before I gathered the tubes of netting. R - after gathering the netting to fit the base.
I attached the gathered tubes one at a time, starting with the widest one, at the bottom, and then adding the middle width, and then the narrowest at the top.
The end result still wasn't quite poufy enough, and I had lots of netting kicking around, so I used more netting to stuff into the large and medium tubes, to create more pouf. (There wasn't room to tuck more into the narrowest tube, which was already pretty puffy on it's own.)
I decided to use a hook-and-eye system to attach the bustle to any particular skirt - so I have large hooks on the back of the bustlepad, and will attach matching large flat eyes to any skirt I want to use the bustlepad with.
This was a very simple, very easy bustlepad, which produces a prodigious amount of pouf for its light weight. Contrary to what I've heard, the crinoline as done here (tubes and stuffed with more crinoline net) seems pretty resilient.