Here's a similar pattern, Aunt Alma's dorm boots. This one is knit in the round, but I found it easier to do this on straight needles. You would just have to sew a seam on the bottom sole and the back of the foot. You could use the stitch count from your pattern to do this if you want. That would accommodate the larger size for felting.
http://www.needlebeetle.com/free/aadb.html