The buttons are underneath the SATA port, you can probably get to them without unplugging anything. If you will excuse the quality of this photo:
I have drawn a red box around the buttons. It is easiest to depress them with a paperclip or a ballpoint pen or something.
Before I knew about these buttons, I had done a few restarts by unplugging the box, taking out the cover screw, disconnecting the battery, then putting it all back together. Boy did I feel silly after I read about the buttons!