How to prevent the doll’s wig from slipping off?

1. Try velcro. One side could maybe be fastened to the head with double-sided tape and the other side is sewn onto the wig.
2. If the double-sided tape isn’t strong enough, you could try mounting tape next.
3. I use T-pins to secure the wigs on my anime dolls. They’re long enough not to work loose and the heads stay flush with the surface.
4. My TPE doll’s wig has little fabric hooks around the inside of the wig. Connect them to each opposite hook so the elastic bands cross over each other, then put head through the middle of bands so the band is the forehead, and other at the back of the head, makes a real tight fit.