3. Flashing the OS.

The output .img file is stored at /bin/targets/(processor)/(sub target)

Here you will find some image files which will be in compressed form by default like openwrt-brcm2708-bcm2710-rpi-3-ext4-sdcard.img.gz so first we have to unzip it.

Now attach an SD card to your PC the right click the img file and select Open with Disk Image Writter.

And select the SD card as a device to mount on.

This will create the required partitions automatically.