I managed to make a couple of skirts with belly bands attached, for pennies, thanks to various US blogs, so thought I'd put up my version of events.
The blogs I followed said to use the measurements from an existing garment with belly band, which meant no guesswork and no wondering which bits to measure. I made mine a tiny bit larger for ease with one piece of jersey twice the height needed, plus hem, and joined at the side to make a tube. I used the softest waistband elastic I could find, which turned out to be buttonholing, made a circle large enough to stretch over the bump, but small enough to sit comfortably above or below, without cutting or falling down:
taking care not to stitch over any pins,
and that's it! I think the whole thing took under half an hour. The skirt's been transformed from a big long droopy thing, to a just below the knee full skirt that has proved essential for weekends and 'smarter' slobbing around at home.
Only thing I'd change now is that as the bump has got bigger, the band wants to sit below it, which means if I'm not wearing the right top, letting it all hang out, which is not my thing, or ride up above it, which is fine unless there's anyone else or a mirror around, as what this does is put all the fullness of the skirt around my widest point and it's the lampshade effect all over again.
A longer band would have corrected this, but how was I to know- and it's certainly not information I will be able to use again in future. Ever.
You could also just make a taller belly band and use it to fill the gap between tops riding up and bottoms riding down, for a fraction of what they cost to buy, just neatening up the bottom, rather than attaching it to a skirt. Again, too late now, possibly. Well, by the time I got round to doing it, it certainly would be.
Next stop is to finish Rich's shirt that seemed like a really good idea at the time....
Finally- I kept the cut off part of the skirt- why???