I know it's late but I just tried what the tutorial say's and it didn't work for me! I found a solution though...
1. I had to create a new folder called MyPaintings in the saved folder as it doesn't exist
2. I had to rename the file so it would end with this ''_ClaimingFlag_IslandSettlement_C.pnt''
Maybe since the guide came out things changed slightly but just by adding these tweaks it worked for me
Also I didn't need to verify any files. It worked even when I minimised the game and put the file in the folder. Didn't even need to restart the game.
Hope it helps!