Go to a store like Home Depot or Lowes and get packages of the cushion flooring squares to put together to make a surface to block the large single piece. These packages of squares have puzzle piece type edges so they hook together easily and stay hooked together until you decide to take them apart. Usually they individual squares are 24 inches square so you would only need 9 of them to make a 6 foot square.
I looked everywhere for these mats. The store didn't even know what I was talking about. Had to order them on-line. They are a great idea to block. Never blocked before but a couple octagons need it.