There have been many threads on the QB already. I suggest you do a QB search.
To repeat what I have done:
Prepare the fabric for accepting the writing. Make a file folder to size of unfinshed block piece and then cut a window on the front side for the actual size of the signature portion. On the back inside of the file folder use a Sharpie type pen to mark a baseline. Give each person the file folder with the fabric inside. Have plenty of extra fabric pieces as many people can't follow directions. It helps if you have several people helping with this and it helps to have extra pens, as they tend to 'walk'.