This is heresy and I'll probably be boiled in oil,drawn and quartered, and the remains burned at the stake.
I recently had some of my air dryed elm warp a little too much for a project. I took the pieces, sized for the project, into the shower. I rinsed the boards down with hot water and allowed the steam of the shower to soften the wood. I stacked the boards by size on a cinder block and then stacked three blocks on top. I let them dry for a week and a half. So far so good. It's been several weeks, and no return of the warp.
Your results may vary.