It doesn’t even have to be much separation, just enough that you can mentally leave it. I work from home but don’t have space to dedicate an office.p, so set up my laptop in my dining room. However I have a deskchair I only use for work, and only use that end of the table for work. That seems to be enough for me to mentally leave when I physically leave it

Unfortunately I get work email and slack on my phone. Slack is not a problem because it’s work only. However maybe that’s why I rarely check my personal email these days