Probably the easiest way to create a slideshow with Flex Slider is by using the "Flex Slider Fields" module, as it doesn't use Views at all. This video shows how to create slideshows from basic multi-value image fields.

Image Field Slideshow

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• Flex Slider Fields

This module simply works by configuring the display settings for any content type that has a multi-value image field. Let's add a multiple-value image field to our Basic Page content type.