Hi Jonathan
Unfortunately there is no simple solution that doesn't require a certain amount of getting your hands dirty with code.
The flexslider module isn't actively maintained and client feedback suggests it is not working as is.
What you describe is actually something that has been requested quite a few times and it is on our roadmap for Views, but I don't have any information about when the feature will be added.
All of the slider functionality that we currently have in Views and in Layouts is for transitioning between posts, e.g. if you have 5 posts each with a featured image you can create a slider based upon those 5 posts and their featured images.
Pretty much every slider plugin I have tested expects you to manually add slides from the media gallery.
You want the slider to automatically pick up the Types image custom fields attached to a post.
The problem is that the slider plugins don't expect to find the images as post custom fields.
I think you will need to craft your own solution using an existing JavaScript slider library.
That's not so difficult. The flexslider comes with documentation about how to set it up here: https://woocommerce.com/flexslider/
Your view will need to generate the markup as per the documentation, and you can add the code to initialise the slider in the custom JS section of your view.
The view loop output (whether you enter it directly in the view or via a content template added to the view loop) would look something like this, assuming your image custom field had a slug of 'slide-images':
<!-- other content... -->
<h2>Here comes the slider</h2>
<div class="flexslider">
<ul class="slides">
<li>
<img src="[wpv-post-field name='wpcf-slide-images' index='0']" />
</li>
<li>
<img src="[wpv-post-field name='wpcf-slide-images' index='1']" />
</li>
<li>
<img src="[wpv-post-field name='wpcf-slide-images' index='2']" />
</li>
</ul>
</div>
All that is missing is adding the flexslider stylesheet and script to the page. In WordPress you do that by enqueuing them from your theme's functions.php file. See the official documentation for details: https://developer.wordpress.org/themes/basics/including-css-javascript/
That is the kind of thing that is required. Let me know how you get on.
