These shoes were really quick and fun to make. Start to finish, around 20-30 minutes. I would say Intermediate Sewing Skills, just because small things are a little harder to sew, and you have to work the stitches in a circle instead of a straight line. The possibilites are endless - check out Lots of Samples HERE (there are a few pictures not of shoes - get through those and then there are tons of shoe pictures).
I found a couple of tutorials and patterns. The one I used is:
http://stardustshoes.blogspot.com/2006/10/cloth-shoe-pattern.html (I altered it just a little and didn't fold over casing for the elastic - I just sewed it inbetween the lining and outer layer).
There is also one at:http://www.tackyliving.com/article.php?id=121 (the difference is that this pattern calls for making a separate elastic casing).
My baby is 3 months old, and these have a little more room in the toes, but are pretty snug in width. I'd say the pattern is for 3-6mo, but I'm sure it is easily altered.