I had my anemone for over a year, fed it twice a week (a mix of squid, clam, fish, and shrimp. I started by making my first cut straight down the mouth and out to one side. After that I spread the cut open, making easier for me to make aclean cut out the other side of the mouth. After it was cut, I set in a quarintine tank for 10 minutes to allow it to suck in some water and shed some excess slime. Then I pulled it out for 1 minute to allow it to purge itself and into the main tank it went. It took about 1 week for it to start feeding again.
This is how I did it. I am sure there are other ways. I had the idea of doing this before I saw Anthony Calfo speak when I saw a LFS remove a blue carpet from a tank and tore a small part of it off where it was attached to a rock and 2 weeks later it was its own little anemone. I certainly needed the motivation from his lecture.