Place your tape measurer on the floor and measure upward until you hit about 2 inches above the bottom of the basin. This gives you a measurement on which to base the fabric height. Placing it 2 inches above the bottom of the basin allows adequate room for the Velcro attachment. Then, measure the circumference of the basin.
Spread a flat bed sheet onto a work surface. Measuring from the hemmed bottom edge to the height measurement you took earlier. Draw a straight horizontal line at this point by using fabric chalk. Cut over the horizontal line with fabric scissors, discarding the excess. This leaves you with fabric that is the proper height.
Measure horizontally from the edge of the sheet to the distance of the basin's circumference. Draw a vertical line with fabric chalk at this point. Cut on the line to trim your sink skirt to the proper size.
Fold each edge in about 1/2 inch. Apply iron-on hem tape along both cut edges of the sheet. Turn the iron to the proper setting for your product. Press the iron onto the fabric so that the tape adheres to the fabric.
Place a strip of industrial-strength Velcro around the circumference of the sink basin. Peel away the adhesive backing and press into place. Place the other side of the Velcro on the top of your fabric sink skirt. Line the Velcro sides up to install around the sink.