This pattern could be easily sized up by using larger needles. Before felting, gauge is closer to 3 stitches an inch. This took me about 4 balls of yarn. Also, you can make the bottom, sides, and top all different colors to use up your stash yarn.

The top of the slipper is knit first, then the sides, then the bottom. I worked this with two sets of circular needles. In theory, you could make it with a set of dpn’s, but it might be a bit fiddly that way.