This video will show you the method used for the cover used by the Bay Area Foam Sports League. Some notes on these however, we recommend aiming for 4 foot by 4 foot cover sizing, and this will net you a slightly larger piece of cover by a few inches.

Also the video uses 1 foot long pieces of PVC for the feet, we recommend making them 2 feet long each, and having either sand bags or stakes to hold them down if playing outside where the wind can affect them.