What you'll need:
Needle felting tool
Needle felting brush
Wool felt (amount depends on size of tree skirt you want)
Cut a circle... if you're doing a tiny tree skirt like mine, you can use a big bowl as a template
Fold your circle in half, and in half again. Cut an arc at the folded point to create the circle in the center for the tree trunk.
Cut a straight line from the outside of the circle to the inner circle (this allows you to get it around the trunk of your tree).
Tear of a thin strip of wool roving and line it up about a half inch from outer edge of circle.
Stab it! Be careful not to stab too much or you will degrade the strength of the felt. (bottom left photo is showing the back of the felt post-stabbing)
Continue laying strips of roving where you want your stripes to be and stab away!
Once you are finished stabbing all your felt, dress your tree!
I actually think I'll be moving this adorable little tree + skirt to my cube at work!