I have a Standard record detail page in which there are sections which include visualforce pages. I'm rewriting these using SLDS to look like lightning. From one VF page I'd like to open a modal which opens not within the section itself but overlays with the standard page behind. Similar to opening a Lightning Action (the modal pops-up over the standard page).
The issue I'm getting is that because the Visualforce page sits within a section of a standard page, when I initiate a button to open a modal it just opens it within the section itself. I've looked at the following http://blogforce9.blogspot.co.uk/2014/01/simple-popup-in-salesforce-standard-vf.html and https://kevansfdc.blogspot.co.uk/2017/02/using-salesforce-standard-modal-in_14.html but could not determine the setting to ensure the modal pop-up instead of just displaying contained within the VF section within the standard page.
Kevansfdc's post refers to a detail page button but I do not want to use a detail page button.