I cut out the skirt as a single strip of fabric, and then cut a second narrower strip for the section below the lace. Using the selvedge as the bottom, I pinned the two strips together with bottoms even and then pinned the lace on top. I cut and folded the top of the flounce into scallops and hand stitched the lace on to finish it.
I'm pretty pleased with the results - the subtle difference between one layer of fabric and two layers is just what I was hoping for.
The underskirt is yet to be hemmed, this will be done with a very wide hem to make it the same length as the overlay, then any adjustments to the length will be done from the top when attaching it to the dress.
I also cut out the sleeve pieces - two layers of net, fabric and the overlay - but haven't started assembling them yet.