All those terms just refer to the way the growth rings are oriented in the wood. A conventional stave is split from a log, unsawed, and the back follows one growth ring. An uncrowned stave has the crown (roundness) flattened off the back, sometimes done to small diameter staves to remove excess crown or to make it easier to back a stave with something like bamboo or a slat of hickory. Plain-sawn lumber has the rings oriented like they would be in a split stave, edge-grained boards are sawed at a 90 degree angle to the rings, and bias-sawn boards have the rings running at a diagonal angle.
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