I made this enormous 12 square foot bulletin board for my story notes. I used a piece of hard foam insulation, cut to size as the base of the board. The insulation is rigid, cheap, and will accommodate all of the poke holes that I put into it fairly well. It would be possible to cover the board with a sheet of cork but I decided to cover it with a large piece of fabric instead. The fabric was pulled tight and taped to the back using duct tape.
Then I mounted the board, which is extremely light, with two long screws. Because it is so light and rigid, two screws is all it took. I slid pieces of hard plastic straws, cut to the depth of the board into holes that I drilled. Then I added the screws that fit into the straws and were long enough to go into the wall stud. The straws and the large washers I used prevent the screw heads from from sinking into the foam.
Notes are hung using straight pins rather than pushpins. Not only are they easier to use but they create smaller holes, extending the life of my foam base. Although I am using plain steel pins, color-tipped straight pins can be used (or these heads can be dipped into paint) for those who like to color-code their pins and/or notes.
Because the pins stick out from the surface of the board, I can also use thread or ribbon to connect notes into storylines so I can see the various routes taken by my characters and how they intersect on my story map.
I intend to cover the edges of the board and screw heads with some framing material. However, a different choice of fabric and the deliberate appearance of screws (maybe shorter "dummy screws that don't go through into the wall scattered around the edges) can give this board an industrial look.