If you write historical romance of the non-closed door variety, sooner or later you’re going to find yourself researching undergarments. I’m sure there are lots of places on the internet where you can find all the information in one place, but one more won’t hurt. My books are set in the 1880s-90s, so that’s the period I’ll cover in this post.
I can’t remember who called the appearance of Victorian women in photographs ‘well-upholstered’ but the description is spot-on. Unsurprising too, once you realize how many layers they had to put on every morning to be considered ‘decent’.
First your well-bred lady (probably with the help of her maid) would put on a chemise:

Then the drawers:

The chemise would be worn tucked into the drawers. Or you could opt for a combination, which was basically the two garments stitched together without all the excess fabric. Then you’d add a corset which would be attached to your stockings with a suspender belt.

Then a petticoat:

Then a corset cover:

Then, if it’s still the 1880s, a bustle:

Or, if it was the part of the 1890s when massive sleeves were in, you need wire sleeve supports:

Give or take the odd sleeve support and varying the size of the bustle, you’d end up looking something like:

There. Now she’s ready to put her dress on. Assuming she still has the energy.