Very nice quilt.
After the first bed skirt I had kept sliding off the box spring on one side or the other, I cut the ruffle off the flat piece that is supposed to cover the spring and sewed the ruffle by hand to the cording on the box spring so it stayed in place. I've made two bedskirts since then, and I also sewed them to the cording instead of using a muslin piece between the spring and mattress. It works great!
The skirt doesn't have to be all in one piece. For a box type skirt, I made two corner pieces, two side pieces, and a foot-of-the-bed piece, and where they came together, I folded the top piece back and made what looked like a pleat.