When I do a build I install the HD only at 1st .... install the OS to the HD on a small partition at the front of the drive. Then I unplug the HD data cable and install the SSD, do the OS install to the SSD. After all is done, I reconnect the data cable.
This way if SSD install gets borked, I can always go into BIOS and tell the machine to boot off the HD instead. Normally tho, you are gonna boot of the HD .... I also put most demanding app or game onto SSD