I have used this method for years and have posted it here several times. I take file folders and draw and cut out a "window" 3/4" smaller than the block to be signed on the front of the folder. That gives you your 1/4" seam allowance and a scosh more. I mark around that window so it is clearly marked on the inside of the folder back. I then cut a piece of fine grit sandpaper the size of the block and glue it over the marked square on the inside. I make several so people don't have to wait very long to sign a block. I always ask someone to man the table so that they can instruct people if they need it. I used to use fine point Sharpies, but if someone leaves the tip of the pen on the fabric too long, the ink will bleed into the fabric. I now use Pigma pens and don't have that problem.
Once you have the signed blocks, be sure to press them with a hot dry iron to set the ink before sewing them into the quilt.
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