One thing I find helps with the corners is to fold the second side opposite from the first. It took me a while to get good at doing it with the fold the other direction, but now it's easy.
A few years ago I was making 6" potholder type blocks for a project at work, needed about 20 a month for a year. I did bias binding on them and sewed them in a circle before attaching. Having 4 corners in 24" of binding really gave me a lot of practice doing them.