Aye, there is a "tried and tested fast way" - hire a woodworker.
OTOH, what kind of wood and how do you want to join them? End to end, end to
face, end to edge, edge to edge, edge to face, face to face, sixty nine?
Straighten the edges with a jointer plane. Takes some technique, but
that's the way they did it in the old days.
Start with a table saw to make sure both edges are as straight as
possible. Then clamp both boards together and plane both edges at the
same time. But they have to be STRAIGHT.
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