This is the underwear for my 1760s-1770s dress. I never got around to making the dress, but some day I'm sure I'll make an 18th century dress. This far I've made the underwear and a stomacher.
The corset is made after a pattern in Diderot's Encyclopedie, which can be found in Nora Waugh's Corsets and crinolines (1954, reprinted in 2000) as well as at La Couturière Parisienne.
Waugh's drawing of the pattern is a bit easier to work from though.

This is how my pattern looks, the measurements of the corset are of course mine and would only fit you if you had a chest measurement of 114 cm, a 90 cm waist and a long torso, but you get an idea of the proportions.

The corset is made of three layers of thin, striped cotton (the same as in the pocket hoops) and a top layer of printed cotton. The top fabric is a reproduction of a 18th century printed cotton that was used for an apron then. The edges are bound with red cotton tape and the holes are sewn with linen thread as usual. The boning is of several types. The most of it it cable ties, but since I have a long torso and some of the boning run almost from the shoulder to the waist point, I needed something longer.The longer bones are what's called "german boning", a semi-opaque plastic boning that can be cut with scissors and come in different widths. For a survey of boning materials I recommend Sarah Goodman's article.
In addition to the bones that run from top to bottom there are also some bones that run on top of the rest of the boning. To get these in place I had to hand sew strips of fabric on the inside of the corset, to create boning channels.

In the pictures above I have no busk since it isn't finished yet. Still I think the corset does it's work in giving me the correct shape and posture.
Under the corset I'm wearing a thin linen smock with machine-made bobbin lace around the neck and sleeves.

In the third picture I'm wearing my pocket hoops, also after Corsets and crinolines. The pattern show how they're made and the size is the same whatever your own size, it's just the length of the waistband that needs to be adjusted