I know a lot of people want to build Walls maps, so I have made a template, on which you only have to build and the four corners of the map.
Download:
click hereImportant note:
Maps made using this template can only be used on MC Zone servers, because all the redstone that makes the Walls work in vanilla is deleted. Also, the spawnpoint is in mid-air, although you are in creative so this shouldn't make any difference.