Soles are covered with natural latex which makes them not slippery.
Wool is a perfect material for footwear, especially for children. It is wear proof and warm. The little foot will not overheat and will not get cold. My little sons are running around in felted slippers all the day.
For little children it is better to make high countered slippers with hook-and-loop straps. But for older it is enough just high countered ones.
These are made to order but slippers can be made in any size. Please, ask if you have questions.
Usually it takes 5-7 workdays to make it and 1-3 weeks to ship.