For cutting anemones I use a brand new strait edged razor blade.
I begin by placing the anemone to be cut in a small bucket of water taken from its home aquarium. I also collect aquarium water in a second small bucket to which I add enough iodine to add an amber hue.
A small square of glass is used as a cut surface. First I cut from the mouth out to the edge by placing the corner of my blade directly in the mouth and then lowering the rest of the blade onto the disk of the anemone. Next I rotate and do the same on the other side.
After cutting, I rinse the anemone halves in the bucket they were stored in before placing them in the iodine water to soak.