"You can add a block that will be position relative, so it can hold the absolute block."
This was your answer, and I know that this is the correct way to do what I want. But I don't know how should I do this. So the question: how (where, in which css) can I add a relative container to any module position? My purpose: when I add a slider module to this position, it appears full width in the browser, like here: demosite