Use the Subzone Template is possible. It takes care of deleting sections, etc. automatically.
When creating an area, make sure to check for all of the criteria below.
If an area doesn't meet one of the below criteria in the Info box, just delete that portion. (IE: no missions = no mission box)
DO NOT delete the Speedwalk or Inflict boxes. Just put None in the Inflict box if no monsters can inflict a status. Put a ? if you haven't checked.
XP RANGES: Do NOT include bosses in the XP Range spot in the area info box. Just put the lowest and highest non-boss XP ranges in there. If there is only one monster in the zone, then the lowest and highest will be the same. (IE: XP Range 350 - 350)
IF A MONSTER ALREADY EXISTS in another area besides the one you add, make sure you add the new location to the monster's page.