Free patterns for fleece slippers are available on Rhonda's Creative Life blog, Leafy Treetop's blog and CutoutAndKeep.net. In addition, a wide variety of free slipper patterns are available on SewPin.com. While these patterns do not specifically call for the use of fleece fabric, fleece is always a fabric option.
Rhonda's Creative Life blog provides a pattern for a fleece stocking-style slipper as well as an in-depth tutorial. The only supplies needed to complete this pattern are ample fleece fabric, scissors and pins, Slipper Gripper or the like, and a sewing machine or serger. This pattern is available in PDF format for three sizes.