Two of the icons of post war Haute Couture have to be the Venus and Junon gowns by Christian Dior. Both gowns are held at the Met museum (Venus. Junon) where they belong so they can be marvelled at into the future. I am staggered that there once was a time when women (undoubtedly wealthy women) would have somewhere to go that required a gown like this.
The sequins are applied to a mesh which would have been stretched onto a frame and the petals marked. The petals would only have been cut out after the embroidery was complete.
Here are some rare photos of these dresses on models.