title: Display loading/splash page in Flask
body: <p>I have a flask app that displays a single page of content, but it takes up to 20 seconds for the content to be generated. It seems to me one way to display a splash screen would be for the main URL endpoint to display a page saying something like 'Loading, please wait...', then redirect to the page that loads the url endpoint with the actual content.</p>
  
  <p>However I can't see how to get this working. If I just write a JS to redirect to the content, the original page disappears immediately so you don't really get to see it at all. How can I trigger a ld of the content while ensuring the loading screen stays put until the content page finishes loading?</p>
  
  <p>I've extensively searched for an answer to this but none of the existing Q/As actualy show how to solve this problem.</p>