It’s quite easy to understand how to solve this challenge, but it’s very tedious to do:
Like everyone else during the event, I used Photoshop to cut the tiles and move them to get the flag. But later, I used that as an excuse to learn Tkinter and made a simple App using Python. You can find the app here!
With this, I was able to solve the image:
And read the flag: FCSC{1283AEBF19387475}