Adding ssd storage on jetson nano

hi Wayne,

these steps seem does not help on our situtions. we are producting Jetson nano in the factory .the ssd is plugged in on the jetson nano carrier board.
i am looking for how to flash the system.img (this assuming is the filesystem and app partition) over the micro usb to the sd and everything else flash onto the EMMC.

could you help me on this ?
Thanks