A great way to learn more about historical fashion is to study original garments. I like to keep a few feelers out on eBay for damaged, stained, and otherwise far-from-pristine antique garments, because they're great for learning historic sewing techniques and taking patterns from!
Today I took a detailed look at this antique Edwardian corset-cover-petticoat combinations. I think it dates towards the later end of the Edwardian period, as its a mere 68" in circumference at its widest point.
It's decorated with lace, pin tucks, and whitework embroidery. Surprisingly, it is entirely machine sewn - even the buttonholes and lace insertion! I wonder if the machine sewing and sloppy seams indicate that this was mass produced, maybe piecework in an immigrant home or made from exploited labor in a factory.
You can watch the full analysis and see all the details of this antique combination undergarment in my YouTube video, below: