Glue the batting which is cut to the same size and shape to the matting board. Allow this to dry. Turn over the matting board and glue a second piece. Both sides of the matting are covered with quilt batting.
(Option for use of aida cloth is to only use batting on the inside of the matting board. The two pieces of batting will them be against each other on the inside of the pinkeep. I find aida cloth works well just as well without batting.)