How do I make my frontpage show content from only one folder?

I have a few ideas based on your snippet, but it would also help if we could see your source repository as per Requesting Help.

Before <article> you need

{{ range $pages }}

and after </div> you need
{{ end }}

Also do you have a layouts/_defaults/baseof.html defined? (If not, the define main won’t work).

And finally, I presume you have files under content/posts so that

picks up pages?

HTH.