This gown might not end up looking over-much like a Poiret, but for the time being it's convenient to call it one.
The concept started with a length of lace whose scalloped edge fit perfectly over Yren's bust for a strapless bodice--just had to tuck a dart into the sides, plus a tiny one in the center front. Then I attached some point d'esprit to it for the skirt. Easy peasy. (Well actually "easy peasy" doesn't cover the difficulty of reversing the skirt pleats I accidentally set in backward, but it wasn't the pleats' fault I set them in that way.)
The idea is to complete the gown with an under-dress of some silky, drapey, gorgeously-colored stuff, with maybe something like a bandeau bodice and a full length skirt. The black lace will tone down the color enough so I can go really bright--I'm thinking a peacock blue-green... Hey, this designing gig is fun!
Thank you to Aneemal and Chad for the help with taking better pictures of Yren. I was astounded at how much better the natural light works!
Since it worked so well, here are a couple other pictures of Yren taken at the same time.