I used a coffee cup to mark the hole in my skirt. I only made the one for my own tree about 20 years ago. I was not to concerned as the pattern I used at the time directed me on where I was putting the opening,. I only wish I still had that pattern. I was able to SITD around the pattern of the quilt. It was much larger than I expected when it was finished. That was a delight. I stay stitched initially around the opening and the circle then did a holiday decorative stitch to finish it off and cover the stay stitching.