Fold the table cloth in half and cut one piece approx 20 X 20. You should have 2 pieces the same size.
Open the box so it is flat.
lay the box over the cut vinyl cloths.
Place a heavy object on top to hold it in place.
Using the marker (mark) the end of the box that has the most shapes and don't outline it; cut it 3 inches longer marking a straight edge across for the cutting line.
Using the marker outline the shape of the remaining edges of the box.
Remove the box from the cloth.
Using the ruler mark an outside edge 1/4 inch larger than the original mark. This will be the cutting line.
Cut out the outside line remembering to leave the one end longer than the rest of the box and cut straight instead of following the shape of the box end.