To create our quilts we used a 11 X 11 square grid with one inch squares. Use the following links to help you create a design that may have been used on an Underground Railroad quilt.
http://www.beavton.k12.or.us/greenway/leahy/ugrr/quilts.htm
http://www.africanaonline.com/slavery_quilts.htm
Once you have decided on a design plan and color your design on your grid to create your own Underground Quilt square.