Is it ok to copy/paste a section of a previous paper of mine into a new one? I'm in the Physics community. I've already published an article on a journal where I've described a solution scheme that serves to solve a certain problem. Now, I've discovered that the same approach can be used to solve a different model. Of course the model, the comments the results, the plots, etc are different, but the technique is the same. So, is it ok to copy the section of my previous article where I describe the solution technique and paste it into the new one? Notice that the old and the new article feature the same identical authors and that the previous article would be, of course, properly cited.
Technically this is self-plagiarism and not OK. We had problems before where we published the 6th paper on a very similar topic and one sentence in our introduction was the same as in another of our papers (there are only so many ways to describe one thing) and it got flagged and we had to rewrite it, which in my personal opinion is just stupid.

However, if it's part of a methods section it is usually tolerated, since it doesn't make sense to rewrite technical statements all the time. For example in synthetic chemistry you would write something like


  All chemicals were purchased from Sigma Aldrich and used without further purification.


Which is fine to just copy/paste.