I've just finished this. The new tree is only 5' high so the skirt is fairly small, about 30" diameter and it's colour matched to the tree baubles.
There's no wadding, just a layer of old flannelette sheet with FMQ squiggles. Eight diamond shaped nine-patche blocks and nine square nine-patche blocks, the extra one is hidden underneath the other one beside the opening and fastened together with large press-studs