Place a piece of craft paper on your work space. Orient the paper vertically.
Place a ruler on top of the craft paper, about a third of the way down. Draw a line against the ruler's edge stretching from the one-inch mark to the six-inch mark.
Turn the paper in clockwise fashion. At each turn, place your ruler at the tip of the line you just drew, and trace a line from the one-inch mark to the six-inch mark until the square is connected by equal six-inch sides.
Lay your cutting mat on your work space. Place your craft paper with the square template on it on top of the cutting mat.
Place your straight edge just below the top line of the square. A straight edge has a cork lining beneath it to help prevent the tool from slipping when you are cutting out your square with a craft knife. You want the straight edge to be as close to the pencil line as possible.
Open carefully your retractable craft knife. Press it into the paper, against the straight edge and along the pencil line.
Turn your paper clockwise, pressing the straight edge just below the pencil line and pressing the retractable knife into the line until your square is completely cut out.