Crayon rubbing or paint can be added to the material after the collage is finished if appeal to sight is desired. Starch is much less offensive to handle than is glue. A smooth, light weight piece of material such as old sheet material or nylon. Paper toweling can also be used. Stick the collage materials to the collage surface.
Starch works well to stick paper, string or some kinds of material to the base.
The whole surface of the base can be coated with starch. String or paper can be placed on the surface. It will stick but is easily removed and put somewhere else. The student can cover and check the picture periodically as it is in progress. When the picture is completed, the material is stretched over the picture, folded under and the edges taped to the back so that the material covering the picture stays in place.