I tried setting it up with @ben’s configuration, but I just couldn’t get it to work — there’s always some kind of conflict.
Either the correct slug gets generated for the URL, or the layout breaks.
It looks like you’re running into the same issue. From what I can see, you’ve managed to get the slug routing working, but now the layout no longer works correctly for the post collection:
…and also not for the individual post layout:
For me, this means I’ll probably have to wait until there’s more information in the Elements CMS manual. And unless there’s a fix for this issue:
…running a blog just doesn’t make much sense for now.