PeopleSoft just published a new Red-Paper that describes how to convert an existing Classic Component to a new Fluid UI Component. It's a great resource for anyone that is interested in learning more about Fluid UI and the steps required to move a Pixel-Perfect Component to a new responsive Fluid UI Component.
The Red-Paper is called Converting Classic PIA Components to PeopleSoft Fluid User Interface. You can find it on My Oracle Support, document Id 1984833.1
There are a few things I want to point out that are in the document.
Of course converting an existing component is only one way to take advantage of the new Fluid UI. Refactoring existing components to optimize them for the different form factors, or building components are certainly possible. In many cases, developers want to leverage existing components to take advantage of tried and tested business logic.