The flat bottom is really helpful at applying even pressure. Now, as the press compresses a surface that large, if the leaf is unevenly loaded at all, it's going to want to tilt and the press itself is going to want to skate across whatever block you use. I found myself wedging the bottom against a stationary board or a curb and two feet to be able to apply pressure without spinning the whole thing.
For what it's worth, if I had the disposable income, I would have gotten a hydraulic shop press and a handful of enormous clamps to hold the pressure. You'd drive the press, then apply the clamps, then set it aside so it's not monopolizing the press. If you have the money to blow and you want to make a whole bunch.
Many people on this forum, especially Bob, have made perique with simpler setups and are very happy with them. Mine is a little crazy, but no one here is going to talk you out of a little crazy if it looks like fun.