If you're looking for a laid back. slice of life Isekai with no real stakes at play this is the one. I'd say this Isekai is unique compared to other Isekais they are usually about a person being summoned to another world to save it or accidentally dying and getting reincarneted and fighting against the threat to that world. In this one we have no demon king to fight against and no monsters that's terrorizing the world.
What this show is mostly about is Ryouma getting accoustomed to this new world he has reincarnated in and trying to fit in, which he gets great help from thanks to the Jamil family that are very genorous to him, the man of the house is the previous duke. As he has only lived in the woods and studied slimes for three years he has no idea how the outside world looks like so he doesn't know the common sense of the world. And since the gods have blessed him with powerful physical abilities and being able to master all kinds of magic he's not your typical 11 year old kid in this world. Since people are not used to seeing a 11 year old kid being able to do what he does he gets quite a lot of "wow" moments from those around him.
Aside from Ryouma getting used to the new world, the main theme for the series is the slimes. Since he has lived alone with slimes for 3 years he has gathered a lot of them, including new species of slimes people didn't even know existed. There's also a girl who's as old as Ryouma called Eliaria who's part of the Jamil family that's helping Ryouma who has taken an interest in slimes which is perfect for her since Ryouma knows everything about slimes. There's also a bit of love growing between them as the series goes on, but it doesn't get any focus throughout the show.
As for the characters, even though Eliaria is listed as a MC, she gets way less focus than Ryouma, the show's focus is always on him and while Eli gets a lot of screen time, the same could be said for her family too. The whole cast is really good, likeable characters with different and funny personalities (and quite a lot of Dio voice for Dio lovers ;)
So this show is basically about the life of Ryouma and his slimes with the Jamil family as Ryouma learns more the outside world and settles in, hope this gives you an idea of what to expect :)
