I've always used weldwood contact cement, I've used it on everything from vinyl tops to headliners to door panels. Any upholsterer I know swears by it. It may be difficult to find, and needs to be sprayed out of a gun, because brushing or rolling might not be economical for what your doing. At the very least a can of 3M spray adhesive should suffice. Spray both pieces of the repair and let "tack", then press together firmly. You can also glue a thin piece of fabric (whatever you have handy) on at least the back to add strength, also recovering the board w/ new material will help hold it all together. HTH