So this post is for sewers out there. I found this link and thought it looks cool. It's on how to mark a skirt hem for yourself. Trying to hem a skirt on yourself is always a pain, our bodies aren't perfect so hemming the same amount all around doesn't always work - often the front or the back is too short.
So this site suggests using a string with chalk on it attached to a door frame and walk around it. I haven't tried it yet and not sure how easy it would be to actually do - I'll let you know when I start sewing summer skirts to see if it really works.
I'm also curious if your floors not being level would affect it. I'm thinking it would work better on straight skirts like the photo and not as much on full skirts, but you might be able to use to mark the edges and use it as a guide. Anyways - Happy sewing.