Originally Posted by HillRider

Unlike a steerer, the bottom of a seat post doesn't have to be cut at exactly a right angle so cutting it by eye is adequate. A perfectly straight cut may be desirable for your own satisfaction but the seat post will work just fine without it.

To the OP: A file will do a good job of removing the flair and, in fact, you should continue to file until you form an inward bevel at the cut end. That will make installing the seat post even easier.