I did this work a couple days ago, but am uploading the photos today.  There is still a little work to do, but the corset is mostly complete after the work detailed here.

I pinned the ribbons to the back panel, using the same proceedure as for the side panels.

View of the pinning from the other side.

I stitched along the seam, removed the pins, and stitched it again.

I stitched multiple rows along the ribbons as on the side panel, quilting them in place.  Then I ironed over the seam allowance on the other side of the back panel.

I folded over the back panel, and top-stitched it in place.  Then I sewed in the boning channels that will couch the grommets.

Before attaching the busk panels, I prepared the hook side of the busk.

Both were then ironed in half, and the peg side of the busk was marked for insertion.

Then it was inserted.

The busk panels were pinned and sewn just as with the side panels and the back panels.

The ribbons were thoroughly stitched down, and the seam allowance for the other side was ironed over.  The peg side of the busk is held in, but the hook side must be inserted before top-stitching.

The busk panels, after top-stitching.

The busk panels are not done, but I want to make the backing bone for the busk before finishing the busk panels.  I intend to match all stitches on the peg side on the hook side.

The boning has been inserted (not shown), but I have not yet stitched it in place.  All that is left is the backing bone, the grommets, stitching the bones in place, and edging the corset.  Last detail will be a decorative bow at the top of the busk.

‘Ta for now.