Simply remove the weight hook at the bottom of the center column and loosen the twist lock to pull the center column out of the spider of the tripod. Next, flip the center column upside down and insert it back into the underside of the spider. Be sure to line up the groove when doing this. Find the height you want and lock the center column. Now you're good to go!
This allows you to position the camera close to the ground while still maintaining a small footprint. Even though your shots will be upside down most photo editing applications should include an image flip tool making it easy to correct this afterwards.