Some stories and genres don't need an ending per se. I think a lot of people get too caught up with neatly tying up stories, and that just isn't appropriate or satisfying with every story; especially if it's slice of life, iyashi-kei least of all, it may not really need to have a distinct or concerted ending. A lot really depends on how you feel about it.
Slice-of-life stories tend to paint a fairly consistent portrait of the characters' lives, and stories true to life usually have small, short arcs. A slice-of-life series, in my opinion, is usually best off leaving the readers with one fond last look, maybe even a sentimental one, at the characters and their lives, before leaving it and closing that window into their world.
I usually enjoy the slice-of-life approach, as it gives creators the ability to experiment a bit and not have to commit to long stories that may not ultimately be where they want to go. It's especially useful when you try something and it's not well-received or enjoyable, and you want to move on to something better. You can!
I'd say just have a good idea of your scope and what you want to do, and since slice-of-life tends to be true to life, you don't really have to be too strict when bringing it to an end. It's like moving into a place, getting to know the people, and then a while later moving away; life continues on for you and them, even if you're no longer so closely involved in each other's existences.
