My bench is a rough boarded affair, but I planed flat, a board about a foot wide by about two foot six inches long to plane on. I screwed some screws in one end as a stop. This has now evolved into a more complicated affair with a series of holes bored lengthways and diagonally to take short pieces of dowel. I can then use a piece of wood in the vice to secure one edge of the piece to be planed with wedges between the dowels and work piece holding the other side, and the end resting against a couple of dowels. The board has two larger holes bored through the centre and is secured by cut off broom handle into corresponding holes bored in the bench. This holds the wood securely. I do not have any holdfasts and have no use for them as I can use a clamp if necessary. Instead of holes, to secure the board to the bench, a piece of baton fixed on one edge could be used to secure it in the vice.
For thin stock I revert to using the screws at the end of the board.
Nigel.