Takes me 45 minutes to an hour depending on the size of the quilt. I have the zipper leaders that I can either sew the backing onto or pin. I prefer to pin it on for some reason.
Then I float the batting and the top stitch the sides as I advance, until I get to the very end. Then pin the end down too.
Not sure why it took 2 hours, although if taking the time to teach how to do it vs just doing it....it could take longer.