10x20 is pretty small and is not really enough to skate on but is enough to teach a small child to shoot or stop and some other basic skills.
I did that last year as that is as big as I could go. I just bought the Redi-Rink from Superstore or Walmart. It is basically a 10x20 bag, you build your frame with snow or wood, fill with water, let freeze, cut off the top and then do some top levelling layers. It works pretty good and is relatively easy.
