The same general drift as a few of the posters already. I haven't experienced anything you could call a flat spot, but have had problems with bulges.
There is a 'witness line' on most tires just above the rim that is a big help to see if it is seated evenly. Check that at about half inflated, and again when you are finished. If it is too high some place, let the air out and see if you can work the tube higher in the tire there. Or just fiddle around a bit. It usually doesn't take too much to get them to come out even.
Good luck with that.