Great care should be taken while doing this as you can easily nick the leaves or another bloom stalk with a sharp knife. I know because I have done it. The stalks are very fibrous and tough.
I recently had a dilemma about how to cut two spent bloom stalks without damaging a third that had come up between the two spent ones.
After thinking about it for a while, I came up with the idea of slipping a plastic card between them. That way I would not damage the new bloom stalk if the knife should suddenly go through the stalk.
It worked perfectly. No damage on either side of my new bloom stalk.
I had another Amaryllis that had the leaves come up between two bloom stalks; one stalk was spent while the other was still growing. This time I found a stiff piece of cardboard and cut a piece about the size of a credit card, then carefully slipped it between the leaves and the stalk; once again it worked perfectly, no damage to the leaves from my very sharp paring knife.