I decided to try needle felting to make a wig for a Monster High Create A Monster doll. I started by making a wig cap that would be the basis for an updo. The photos below show it from different sides.
The wig cap kept slipping off or into wrong position, so a peg for keeping it in place was necessary. I used a strip from a 0.3 mm thick metal sheet.
As glue wouldn't have kept the metal strip in place, I cut a small piece of felt, made a hole in it and pushed the peg through.
Then I put the peg in place, spread glue to the felt, put the wig cap in place and pressed it down to the head to make the peg construction stick inside it.
Here is the inside of the finished wig cap.
Then I attached the actual hair inside the edges of the wig cap. I used coarser wool for the wig cap and mohair for the actual hair.
This looked funny and I can imagine all sorts of funny hairdos you could make this way.
However, this one was about to become a very formal updo. I collected the hair and attached it to the top of the head. Then I made the bun and attached its bottom to the top of the head as well. The hairline of this wig is maybe a bit too high, but it's good enough for a first try (and my second needle felting project ever).