[SCA-BMDL] carpentry query: avoiding wood warp

[Logan]

Good day all,

I'm replacing my yurt's inconvenient door-flap with a proper wooden door, but I'm concerned about warping.

For packing reasons, I want to make a dutch door (separate top & bottom).
I was going to just make it out of treated plywood, but that warped severely when I was building my roof-ring.

Is there any way to avoid warping without adding too much weight?
I'd like my door halves to line up with eachother and their respective frames.

Thanks,
-Logan / Stanislaw