Have you checked out the clog thread??
I know, I know, it's really long, but many basic questions are answered at the beginning. :D
The adult clogs are knit on 24" US13 needles. Personally, I'd rather make the clogs bigger than my shoe size, 'cause I'd hate to felt them to the right size but still have stitches showing. (I'd rather have to felt them longer to ge tthem to the right size and lose all of the stitch definition.) And yes, the pattern does have instructions for felting. Between all of us we've made 34059853 pairs of clogs, so if you need further help, of course you can always ask!