The following illustration shows how you should set up the paper for coating. I find it is best to use a piece of plate glass as the base as it will provide a flat surface.
Plate glass is fairly inexpensive.
Have you shop sand the edges. If you don't you may find yourself dripping blood all over the place if you have to pick up the glass and move it. Next you want to add a couple of sheets of newsprint. 2 or 3 is enough. Any cheap paper will work.