Essentially, I added 1" strips of elastic to support the weight of the back.
Many other Holdo costumers talked about putting a zipper down the center back. While I included a back seam, I didn't put a zipper. I attached the back left part of the neck piece, the part above the rectangle drape, to the back. I put one piece of elastic just to the left of the center back, and one as far to the left as I could put it while still keeping it hidden.
Along the right side of the back, I added hooks on the edge, and flat eyes along the bottom of the neck piece. Below, you can see the hooks on the edge.
Here's a top view of the hooks and eyes. Note how the color looks totally different that in the above photo, and how I somehow ended up with an extra hook.....
When I put on the dress, I have to wrap the right side around my neck to close it, as you can see below.
To avoid any lines, I got a seamless bodyshaper to wear underneath. In order to keep the white elastic from showing, I safety pinned both sides in center front.
. Then, the longer two pieces get wrapped under the center of my bra, and pinned back on the elastic. I ended up using a strapless bra, to lower the risk that my straps show (might look for clear straps for the bodyshaper), and the elastic helps hold it up nicely.
In the above picture, you can see approximately what it would look like. I use a giant safety pin, not a straight pin!
I left the ends of the right side elastic, the parts that go down the back, long. I thought I'd need to add hooks or snaps to anchor them, but I don't think that'll be necessary.