I remember reading many years ago (maybe 50) that the best way to treat 
your wood for a projects was to stand the boards vertical against a wall 
with each layer spaced a bit at the bottom to allow air movement for a 
year. Then it will reach the equilibrium of the space/area where it will 
live thus minimizing unwanted movement. You will never stop the 
movement. I remember building a table top from red ceder 2x6 to use at a 
wood show with a set of those folding legs under it. Since it was a 
tight time scenario only the top side got varnished before we left to do 
the show. By the time the show was over the center of the top was about 
an inch higher than the edges which worked great for people walking 
around the table but was not the intention. Later we sanded the top down 
again and when it flattened out we refinished it on both sides and still 
use that table for displays at shows.

Nick