Bending birch plywood

I have a largish piece of birch ply (120cm by 60cm) that warped — one corner is 2cm off the flat plane. I cannot replace this piece, so I’d like to try and bend it back to a flatter condition. I assume that heat and steam, or both, might be how to do the trick, so I’d like to ask:

• if I apply (dry) heat, should I apply to the cupped side or the side that cups out?
• same question for steam: on the side that cups in or the side that cups out?
• what about using dry heat on one side and steam on the other?

I can easily live with the piece cupping a it towards the non show side. I know I could just try and see, but since I have a 50% chances of getting it wrong I’d like to improve my odds!