Tear a sheet of parchment paper that is slightly larger than the pan.
Fold the paper in half, from bottom to top.
Fold the paper in half again, this time from right to left.
Fold the top right corner down to meet the bottom left corner.
Fold the top edge down to meet the bottom.
Turn your baking pan upside down and place the folded "point" into the center.
Make a cut just inside the edge of the pan; continue cutting in a slight curve.
Open the paper up - you should have a circle that fits perfectly in the bottom of your pan.