I got back to working on the strapless dress today.
I started by sewing the back seam on both the under layer and the chiffon.
Then I pinned it in a few places to prevent the layers from slipping apart. And I pinned the pleats in place.
And I sewed the pleats down with a 1/2 inch seam.
Ok it is a little crooked but as long as the seam attaching the bodice and the skirt is on this seam or further in it won’t show. I Know I am doing many of the steps out-of-order, but it will look the same when it is finished, and it makes sense to me.