I measure the distance from the pin to the bottom of the skirt with my seam gauge. I then mark a line with my Mark-B-Gone pen at that location and work my way around the entire skirt (about 1 inch apart from each other).
Iron the bottom of the skirt up 1/4” all the way around.
Now iron the bottom up 1” or to the first line that you marked on the skirt.
Fold back the fabric like I did and begin stitching with your hem stitch.
Align your presser foot so that the fabric, to the left of the fold, barely gets caught by the needle.
This is how the stitch should look when finished. You can see that the zig-zag just barely caught the fabric.