Mysterious slate puzzle solution in Pokémon Pokopia

As you dig up artifacts in Pokémon Pokopia, you’ll find mysterious slates which don’t have an explicitly stated use, but do have something to do with… Unown? These are part of a larger puzzle with a great reward, if you find them all and place them in their correct positions. There are 27 mysterious slates to find in total, and you’ll need to slot them into the right spots to complete a mural on the wall.