In the end, a slice of life just means a genre that revolves around things that could actually happen. So the key is just to tell a story. Write your characters, and let the readers see glimpses of their lives. You don't have to write from the lives of anyone you know or know about, you could make the story combinations of all of these, or even bits and pieces of things you've read about on the internet.
I think to a certain extent every story is written this way. I certainly don't have a single story that doesn't have at least some part of somebody's real life that inspired it, but they aren't inherently people I know closely.
For instance:
- I have a story where illiteracy is a big theme. I myself can (obviously read) but while no one I'm friends with personally is illiterate, it's a big struggle in my country and thus inspired the struggle of characters in the story.
So my biggest tip would be that literally ALL of life is at your disposal. but I get the struggle, as I'm currently rewriting a series, actually two different stories, I started the ideas for when I was 14, and reworking the characters was tricky. I had to overhaul personalities and details to add depth to all the characters, but if you look at it as a game, it's really more fun than it is stressful.
that said, I am actually working to be a writing teacher rn, so I don't mind giving people more in-depth help. If you're interested you can dm me through Tapas with any questions.