I&#x27;ve had a lot of luck throwing something together in Bootstrap or similar, and then when a designer gets involved with the project, they approach it as more of a redesign: they can get familiar with the app, understand what it&#x27;s trying to do, and then go from there. Paper, in my experience, doesn&#x27;t adequately communicate some things (for instance, more complicated UI interactions are somewhat hard to model in a reasonable way on paper).