Referring to the position of an element in modern (responsive) design

This is such a common and basic issue that there must be an answer somewhere already, but I can't see it, so I'm wondering if I'm missing something. Should we avoid referring to the position of an element when we are not 100% sure that the layout is completely fixed (which is never the case nowadays)? What should we do instead?

Example: "Please fill out the form on the left", or "You can add a new block from the panel on the left". But how do you know if it's on the left? It might be on the left on a desktop device, but it might be above or below on mobile devices, for example, as it commonly happens because of responsive layouts.

I can think of at least two possible approaches:

• Don't mention the position, and let the user figure out where the element is. This might be obvious in some cases, while in others the users might have to look around a bit.
• Provide different messages in different layouts, so on desktop you would have a paragraph saying "on the left", and on mobile that paragraph would be replaced (dynamically or with media queries) with one saying "above (or below)". This sounds like a pain to implement and maintain though, a lot of work for nothing.

However I'm not sure if there's a standard or a best practice to solve this basic issue.