Behold, the chair in question . . (boring!) (and ugly!)
Those of you who sew will have no problem figuring out how to do this. Those of you who don't (like me) can fudge it (like I did). The bottom piece is just one layer with a ruffle around it--it sits there looking pretty like a well-trained, proper Victorian Miss is wont to do. If desired, one can add ribbon to tie it securely at the legs in the back (the seat cover, not the proper Victorian Miss). Or, you can make a case for filling so that it's more comfy. This chair is mostly forced into service as a step stool and used to do a lot of hanging around looking ugly during its off hours. Now, when busy loafing, it at least earns its keep as an object of beauty.