Drawer parts were cut some time ago allowing them time to settle before planing them to final dimension. The pieces must be as close to flat and square as possible before assembly or it will be difficult to get the drawer to slip perfectly into the opening. Perfection, to be honest, is unattainable. After all, we're dealing with wood here not metal. Wood moves. It expands when humidity rises and it shrinks as the air around it dries out. As I'm building in the dry season this drawer will be fit a little loose so that it won't be seized shut when it expands in the height of summer. The best you can do is try to reduce wood movement's effect on the piece. I learned the hard way that ignoring wood movement or worse trying to restrict it, is a bad idea. I built a table once that broke the rules and it began to self destruct within weeks of completion. Now I engineer each piece utterly submissive to wood movement.
When I hear a cracking noise in the middle of the night I rest assured that one of my pieces hasn't started to come apart. "Must be the boogie man" I think to myself as I drift back to sleep.
