When painting with watercolor top of the paper is usually supported in some way so it allows paint to flow toward you. If you want paint to flow any other direction you need to move the painting. Most of the time paper is stretched on some kind of waterproof surface (I use acrylic sheet)  so with larger formats becomes heavy and awkward. My plan was to try to modify camera tripod to support the painting and allow movement in all directions.. It looks like it will work.