1. Lay out a preprimed canvas with a 1-inch allowance on all sides for finishing the edges. We started with 3- by 5-foot canvases (about $8-$10 each at an art-supply store).
2. With a foam paint roller, apply one coat of acrylic latex paint for your background color. Be sure to cover the entire front of the canvas. Allow to dry completely.
3. Using a sturdy, nonmarring tape, hang your canvas on a flat, vertical surface in a room that can be darkened, so the projected image will be easier to see.