If not specified by the manufacturer, it is recommended to have at least a 6 inch apron of protection around the fire pit. In your case, that would mean a 44" x 44" square. Unfortunately, we do not offer a square deck mat in this size. We do offer the Goods of the Woods 54 Inch Round Protective Deck Mat - Black
, which would offer ample protection. I apologize that we do not carry a square mat in the needed size.