Try these links and see if any of them are what you are looking for. I don't crochet, but these are some that came up in a google search. Foot length is mentioned in some, but not all.

http://www.crochetandknitting.com/slippers.htm

http://www.bevscountrycottage.com/menslippers.html

http://helpinghearts0.tripod.com/nasupport/id14.html

http://www.bevscountrycottage.com/slippers1.html

http://www.crochetandknitting.com/slpprs5.htm

Jilla