In doing hundreds of hexies for this baby quilt that I'm working on I have discovered a tip in creating an even seam allowance all the way around.
Starting by finger pressing two opposite sides at the same time, preferably with the grain.
From here just make your folds and basting stitches as described in my previous post, making sure to line up by pressing your first sides periodically.
When you get to the opposite side from your start, lift up that side and make your fold (I'm slightly OCD and like all of folds going the same way), and continue around following the same pattern.
Look at that beautiful hexie! Quick, easy, and nicely symmetrical :)
If anything wasn't clear please let me know and I will clarify. And, if you're working on a hexie or English Paper Piecing quilt, I would love to see it!