My references state that cottonwood seeds require "no pretreatment". So, yeah, basically stick 'em in the ground and water. I would think they shouldn't be planted too deep (references didn't say anything about that), as nature would distribute gently.
The down side here is that you will be growing a cottonwood that produces seed.
If you want to try an experiment, find a seedless cultivar that you like and take a cutting from it. They root readily, evidently with greater success if taken during July/August, and you would then have a seedless variety.
Just a thought.
Sylvia