I'm thinking he wants the back board of the seat frame, itself, to be
bent, not the backrest/leg support to be bent. Caned seats often have
curved seat frames and the curves are usually simply cut from straight
boards. Even Sam Maloof cut/carved/molded curves onto some of his
wood pieces, rather than bending boards to conform. For that small of
board, bending is an overkill operation for that application,
especially if other connecting boards are not bent/curved.
Cut a straight board to the curve you want, otherwise you have the 2
options mentioned above: Steam bending or laminate bending. Also, to
my knowledge, air dried wood is most appropriate for bending, than
kiln dried wood.