I’m sorry the way you described your issue makes it seem like you’re having a CSS and/or Masonry layout issue.
If what you really mean is having a fixed set of content files and only updating their summary then have a look over here.
Or if what you really mean is displaying a fixed set of posts in reverse order for your grid on your list.html you can easily achieve this with range so that when someone makes a new post it takes its position in the “fixed grid”.
Other than that maybe someone else can understand your issue better than me.