Samsung SSD Firmware Update Power Cycle on MBP
The back cover of the MacBook Pro does not need to be on in order to operate.  You can even have the drive brackets removed.  Simply use a piece of non-conductive tape (I've used blue painters tape) to temporarily hold the drive in place.  I've also found that this works best at the edge of a desk or table with a towel or large mousepad for the MBP to rest on when I have it inverted.

If you are required to power cycle the drive, carefully turn over your MBP ensuring you don't close the lid,  pull the drive up, disconnect and reconnect the drive's SATA connector.  This will power the cycle the SSD.  

Once that's done, you can turn the MBP back over and continue the process.