For my money, Aria is one of the best iyashikei slice of life out there. And what really elevates Aria from a run of the mill SOL show to a top tier one, is the setting.
All three seasons of Aria are set in the future, and we watch the character’s lives in “Neo-Venezia”, a city in “Aqua”, which is the anime’s name for Mars. Furthermore, in this universe, the characters call Earth, “Man-Home.” Already from the beginning, the anime has unique terminology and is set in a strange location which we are never given a long exposition for. Instead, we get to explore the culture and the setting of Neo-Venezia along with Akari, our main character.
As the name would suggest, Neo-Venezia has resemblances to the city in Italy, Venice. Because Mars is a planet that is filled with water, the architects of the planet have made a large city with the exact same concept as Venice, in which there are no car lanes or bicycles, but instead bodies of water where gondolas are placed. The main cast are all gondoliers, and it’s great because being able to see the great scenery and explore the lives of gondoliers.
Of course, the setting is nowhere near as important as the characters of the story or the music, since they are what truly carry any slice of life show. But the reason why the setting in Aria is so great is because it makes the show interesting. Iyashikei anime have no real plot, and that’s the point of an iyashikei. Something to watch just for relaxing purposes, with no story and no stakes in the plot. But what happens often as a natural result of this is that the show is boring as hell. How Aria manages to prevent that is by having a really interesting setting, that we viewers get to slowly explore through the 3 seasons of the show.
Another good example of a show which uses a similar tactic in order to keep the show interesting is Flying Witch, where one of the main girls is a witch, and although many parts of the anime is not magic or fantasy related whatsoever, we’re constantly kept entertained by the occasional magic elements of the show.