Thanks for your replies. Buying planer/joiner is not an option. No space and can't justify as a hobbyist. I wish there is a shop near me where I can rent the area by the hour. 
@SMP, @CWWoodworking,
Would gluing multiple sheets of plywood be more stable than using dimension lumber? I am also thinking of adding some sort of metal ribbing on the backside to help it stay flat, al though I have not found such a product yet.
Thickness: 1 to 1.5 inches
Material: Softer wood preferred (again, due to limited tools)
Finish: paint
I don't expect this to be perfect. I just wanted to make it as best as possible with my resources. I have built 9 foot barn door, which one is showing slight bowing, but it doesn't bother me too much though.
Thanks!
@SMP, @CWWoodworking,
Would gluing multiple sheets of plywood be more stable than using dimension lumber? I am also thinking of adding some sort of metal ribbing on the backside to help it stay flat, al though I have not found such a product yet.
Thickness: 1 to 1.5 inches
Material: Softer wood preferred (again, due to limited tools)
Finish: paint
I don't expect this to be perfect. I just wanted to make it as best as possible with my resources. I have built 9 foot barn door, which one is showing slight bowing, but it doesn't bother me too much though.
Thanks!