Measure the trunk of the tree so you get a nice fit. Find a circle that looks good with a little extra room for the binding to go around. Take a piece of construction paper and cut the circle out and and place the paper around the trunk to see how you like it. If it looks good, trace the circle on your skirt with a frixion or chalk pen and stitch 1/8 in from the line on the quilted skirt before cutting out the circle. You can always cut the circle bigger if needed but you can’t put the fabric back if you cut it to big to start.