This is a very simple pattern for cute felted booties! It is in CRAFT Magazine: Volume 05 (November 2007), p. 114.

Gauge is not given for this pattern, however, pattern adjustments for different shoe sizes are. I imagine that, since these are felted slippers, sizing can be a bit flexible.

The pattern suggests “any wool yarn that will felt.”

If you have trouble figuring out how to fold these slippers, the pattern author has provided a video on YouTube to demonstrate the fold.