Super easy, with a clever shaping. We’ll see about the felting - this will be a first attempt.

4/26/11:
Felted beautifully, but because I use a condo washing machine with no controls on it, it didn’t felt enough. However, it will fit my grandson perfectly, I think, so that’s ok. I’ll just make the next pair smaller. (Or it may be that Fishermen’s Wool doesn’t felt as much as the recommended wool.)

These $100 Ugg slippers are very similar: http://uggaustralia.digby.com/shops/web/UGG?cmd=item&itemId=5125-BLK-05Black&vendorId=91

4/28/11: Wahoo! I ran them through a full laundry load and added one pot of boiling water - they felted down to exactly the size I need (I removed them after the spin cycle had run for just a little bit).

Note: first felting - got about 11 1/2- 11 3/4” length. second felting - about 10”. Mom said she’d love to have a pair, so I shipped these off to her, as they’re the perfect size for her now (& still a smidge too big for my daughter).

Photo 1 is the final pair (wet). Photo 2: before and after the 2nd wash (size comparison). Photo 3: the larger pair after one wash only. Photos 4 & 5: before any felting at all.

Had a fair bit of yarn left.