Reference management software: Zotero 7

You can create a reference list without first adding citations to a document.

First, select the citation style you want to use in Zotero Edit (Windows) / Zotero (Mac) → Settings → Export → Default Format. Then select the citations in your Zotero library, right-click, and select Create Bibliography of Selected Sources. 

You can see which style is selected for creating a bibliography by going to Edit (Windows) / Zotero (Mac) → Settings → Export

Once you have selected your citations, you can drag and drop them into a document. This will create a plain text bibliography without any connection to Zotero.