Yes, it is very simple. The picture shows the story. All shapes of canes can be cut with the slicer. It has a solid hardwood base, with a clamp to hold it firmly to your work surface. Yes, we have cut ones even smaller.
Raw canes work too.
I notice that the cane in the picture is square. There is a tiny bit of deformation due to the pressure on the round cane, but this is easily manipulated back into shape when you pick up the slices. I do about half of my canes round, and half of them as squares, and it works very well for both. Construct a cradle around the bottom of your round cane using scrap clay. Then, slice your round cane with the square bottom.