I was going to suggest doing a dresden plate -- you can either use a single piece of fabric or work with a strata and you can make them any length you need. I did one for my DD 10 years ago -- made the ends pointy and did QAYG. It took DD longer to pick out the fabric than it did to make the tree skirt (hers was 60" in diametere which exceded the length of my ruler so cutting was a chore). I did not use a pattern (I do that often).