Select a canvas large enough to hold the mask while maintaining aesthetic appeal. When choosing the canvas, consider whether you'll paint a background for the mask.
Place the mask on the canvas to test whether its back will lay flush. Use a rasp to gently remove excess clay until the mask sits flush with the canvas (see Tips).
If desired, paint a background pattern or color onto the canvas using acrylic paint. Allow the paint to dry for at least three hours before continuing.
Place a thin bead of weather stripping cement along the back edges of the clay mask. Place the clay mask onto the canvas, applying slight pressure. Hold the mask in place for about one minute. Allow the glue to dry for one hour before moving the canvas again.