How to get filenames without dates

[Frank]

date in filename is a convention you have to stick to with Jekyll.

How can I get jekyll to render a collection other than posts on the index page?

The same way you would with posts, except you loop over your collection instead.

{% for article in site.articles %}
  <h2>{{ article.title }}</h2>
  ...
{% endfor %}

see Collections | Jekyll • Simple, blog-aware, static sites

Is it possible to automatically set the slug from the folder that the article is in? If my article is in _articles/my-article-title/index.md, I would like the slug to be my-article-title.

You can try:

collections:
  articles:
    output: true
    permalink: /:collection/:path

see Permalinks | Jekyll • Simple, blog-aware, static sites