A light box is the easiest way I've found. I do hand quilting and have marked most of my quilts that way. I have very few stencils but several books with quilting designs. I just made my own. An old wooden box, borrowed DH's trouble light for inside, and a piece of glass on top. Any light you can put in the box and Plexiglas will work also. Tape the pattern on the glass, lay the quilt on top and mark. The only problem was that the glass would get hot so would have to turn off the light and let it cool.