Measure one side of your table from corner to corner. Write down this measurement and double it to allow for your gathers. For example, if one side of your table is 42 inches, double that number to 84 and write it down. Complete for all four sides of your table. Add all of these numbers together and add two inches. This is your width measurement.
Measure the length from the table to the floor. Add two inches to this measurement and write it down. This is your length measurement.
Cut out your skirt piece. Your skirt piece will be as wide as the width measurement you wrote down and as long as the length measurement you wrote down.
Hem the bottom edge of your elastic skirt. Turn up 1/4 inch of the bottom raw edge toward the wrong side and iron into place. Turn up an additional 1/2 inch and iron into place. Pin into place and hem using a 1/4-inch seam allowance around the entire lower edge of the fabric. Repeat with the top edge of your elastic skirt.
Measure the original circumference of your table around the edges. Cut a width of elastic 1 inch longer than this width. Pin one short raw edge of elastic to the top short edge of the elastic skirt; pin the other short, raw edge of the elastic to the opposite side of the elastic skirt.
Pin the elastic to the top edge of the skirt, stretching the elastic as you go. The stretch of the elastic will create gathers in the fabric, and it is helpful to use as many pins as you feel necessary in this stage. Adjust the elastic and the fabric so that the gathers and the elastic are even from edge to edge.
Change your sewing needle to a ballpoint sewing needle. Sew the top edge of the elastic to the fabric with a 1/4-inch seam allowance, taking your tie and stretching the elastic as you go so that the fabric is smooth and tight. Backstitch at the beginning and ending of your seams. Repeat on the lower edge of the elastic. Remove your pins.
Change your sewing needle back to a standard sewing needle. Pin the short edges of the fabric with the right sides together and stitch with a 1/2-inch seam allowance to close your elastic skirt. Backstitch at the beginning and ending of your seam to lock in the stitching. Turn right side out and press. Place over your table with the elastic lined up at the top edges of the table.