If it's a cutout, scroll saw gets my vote. However, if it is not, then a router seems the better answer. With four pieces it might be a problem cutting out the shape and still having the back support a person properly.
you want fast..Bandsaw would be fastest.
After a bit of practice should be able to crank one out pretty rapidly with a chainsaw.maybe not...
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Plus those bits are expensive. The cheapest alternative would be to use a guide bushing to follow the pattern with a straight bit. Some straight bits have a shear angle on them which will leave either the front or rear edge smoother. Next up would be a compression spiral with guide bushing, a little cheaper than the bearing guided spiral. No matter what you need to cut the piece out close to finished size. Not doing that as Stick said won`t be any faster and it will be way more costly.SURE...
the bit won't last very long...
be slow too...