How do you stop looking flaws in others?

I don't do that unless I'm attacked or I see someone bullying someone else.
The best wat to stop doing that is to first look at yourself, ask yourself are you truly better than or above this person. It makes you stop & think...

I'm the same way i try not to be but I've noticed it's usually my own self insecurities i notice on other people

I don't. I ignore everybody. Life is easier and much less aggravating that way.

Concentrate on your own flaws, which is what that behavior is avoiding