Once I had made sure that my foundation toile fitted properly and very snugly, I made it up properly using a satin coutil fabric. Coutil is the traditional fabric of corsetry, it is very densely woven and has almost no give in it at all. The satin coutil I am using is made of viscose with a cotton backing.
I decided to use the shiny side of the fabric against my skin though usually a separate lining would be sewn over the foundation. I therefore had to join a skirt lining to the foundation which I did by lapping a dress satin over the edge of the foundation to avoid a bulky seam, and finishing it on the inside with a strip of lace so that it looks pretty and tidy.
The inside of the foundation is closed with hooks and eyes as you can see here. The dress will close with a concealed zip. It is a bit of a job to line up the dress with the foundation and I am still researching the proper way to do this. Here, I lined up all of the seams but left the right side seam of the dress wider so as to be able to close the zip of the dress over the foundation. I'm actually not sure if this is the correct way to do it and think that next time I do this, I will make a back fastening (rather than a side fastening as this is), and make the two back panels of the foundation from powernet which is stretchy. It's what bra straps are made from.
Once the foundation is complete, it is attached to the dress as described, by matching the seams. I have finished the top edge off with satin bias, for no other reason than it is easier than contemplating sewing it right sides together with the boning in place, and then turning it right side out! I am already used to binding raw edges of corsets in this fashion.
All in all, I am pleased with the fit and the effect, and here is the edge of the foundation fully sewn into the dress underneath the zip, all neat and tidy. It feels very posh!