You will see on each side of the stock body there is a small button. Pull the UBR back to the fifth notch. Press the button on the LEFT side of the stock to retract the stock to the sixth setting. Now press the button on the RIGHT side of the stock while pulling the retraction lever. The stock body will slide off the tube. Use a flat head screwdriver to remove the screw at the end of the tube, and pull the cheek rest off the tube. Unscrew the tube from the receiver.
*Not sure how far you wanted to go, so I went all the way.