Monoprints come in all shapes, sizes and ways of being created. The vast majority of these prints are derived from laying, or even painting, ink (waterbased or oil based) onto a plexiglass plate in a myriad of colours and then possibly scratching away or moving the ink around with a scraper or comb. Some prints then have hand carved stamps printed on top of the paper image after the print is pulled.
Another method of mono printing I use regularly I have dubbed the Ying-Yang Monoprint. The plexiglass plate has a thin layer of oil based ink or paint, a sheet of paper is laid on top and a drawing is created using just the touch of the pencil on to the paper. Once the drawing is done it gets peeled away. Another sheet is laid on the plate and this one is burnished or rubbed to take the rest of the ink off of the plate. The first print is just the line drawing , the second print is the negative of everything but the line drawing.