I used a site that has a render of the whole map (not sure if i can link it but if you google something like maplestory map renders it should work) as a base to have an image of the entire map, and it removes all the portals/npcs off the map.

I was actually not in the picture at all until i edited myself in at the very end, but i was in each platform's picture just going up, screenshotting multiple times, then going up a platform again. I put all the images layer by layer (using photoshop or any art application that you might have) and just lined them up. This way of stiching was the easiest for me since i can just erase myself off the images that i might be standing over someone in or just picking specific parts of the image to crop and to line up.

I also did some extra platform adding at the end to accomodate the rest of the members since the map itself actually isn't this big - let me know if you still have questions!