Short of a foam padded box made of 1/4 inch steel plates, with welded on hinges for the 1/4 inch steel plate that covers the screen when closed, there's only so much you can do.
I know nothing about that particular smart phone, as I don't have one. But I do have an iPod Touch with a similar screen to protect, and I found early on that Zagg shield film does a really excellent job of protecting from scratches. About a week after I bought my first iPod Touch, and before I put the film on it, I dropped it behind a pile of gym mats, so that it slid face first down the cinderblock wall behind the 4 foot high stack of mats. Guaranteed to scratch the screen, and it did. I was annoyed. I've had two other iPods after that one, both with the Zagg film on them, and their screens have benefitted greatly from being unscratched to this day. In spite of there being no improvement in my co-ordination or tendency toward the dropsies.