Flatten 3/4" She Oak board?
 

Hello all,

I've made a red She Oak baffle for a loudspeaker face, and I was about
to glue it to the maple veneered MDF carcass when I noticed it is bowed
across it's width. It is about 18" long by 6" wide and is warped such
that ends are upturned about 0.5mm at each end -- enough to be
noticeable. Is there any way I can flatten it without using a planer?
Wetting, clamping, steaming or some kind of ritual sacrifice perhaps?

Thanks for any advice,

Thomas Hood