Recent Posts in Slider instead of Featured?

Yes, you can show recent posts instead of featured posts, please provide the theme or plugin, you are using, then we can give you the exact solution to it.

I use untitled theme with (i think?!) the flexslider.

Untitled’s slider uses the featured tag. You can always assign a “recent” tag to the posts you’d like to have in the slider:

To set up Untitled’s Front Page Slider:

1. Navigate to Appearance → Customize → Featured Content.
2. Enter the name of a tag.
3. Click the blue “Save” button at the bottom.
4. Create a post with a featured image that’s at least 1024px wide.

Give the post the tag you declared in step 1. Jetpack is required to use the slider.

It isn’t possible to easily alter the slider to display recent posts automatically, since it relies on the featured-content tag to function.