Clean way for flashing factory image on Samsung Galaxy Nexus?
Yes, this is the correct and official way of flashing

Be aware though, that no matter which way you flash, you can still break your phone

For example, you're in the middle of flashing your device, and the USB lead comes out - bricked device.

Or you're flashing, and you have a powercut - bricked device.

So, the moral is that there is no completely 100% safe way of flashing a device.