He touched on a lot of topics.
On killing off characters (which shocked me several times in the series): “I think there's a certain moral obligation, almost, to give one reason. If you're going to write about war, which my books are about, wars are nasty things. People die in wars. People get maimed in wars, and many of them are good, likable people who you would like to not see die. And I think it's sort of a cheap, easy way out to write a war story in which all the heroes, you know, happily go killing the enemy and maybe they have a few close calls, but no one ultimately dies. So that's one reason. But the other reason besides that is also my goal as a writer is to really make my readers experience the book, not just read the words but to feel afterwards almost as if they've lived it. I want to read it to be afraid. I want to read it enough to know, my God, is this character that I'm identifying with and reading going to survive this thing?”
On whether he is a plotter or a pantser (which he calls architect and gardener, which I quite like): “Yes, there were a few of those. You know, I struggled with that for a while, and I finally came to terms with it. And talk about writers being two kinds of writers: the architect who plans everything out ahead of time and, you know, out in the lands. And he has his blue prints like an architect does, and he knows where all the pipes are going to run and how many rooms there are going to be and what the roof is going to be and the dimensions of every room before he drives the first nail or writes the first word. But there's also the gardener who digs a hole and plant something and waters it with his blood. And I'm much more of a gardener than I am an architect in literary terms.”
There’s a whole lot more, which you can read here.