Note, since I recorded this screencast, I have been leaning more toward using the Paragraphs module for implementing structured modular content rather than ECK.
A few months back, I read an interesting blog post by Chapter Three about something they call the "Slice Template." I was really inspired after I read that, it struck me as a whole new paradigm for content creation, that of "structured modular content." At the same time, I was working on a new Drupal 8 theme and build where my objective was to create something that would give content creators lots of flexibility.
When I've had discussions with content creators in the past, more often than not, the one word that kept coming up was "flexibility." In turn, on site builds, this lead to doing some really wacky things all in one wysiwyg.
In the meantime, I had been playing around with the Paragraphs and Field Collection modules for Drupal 8 but after reading Chapter Three's post, I decided to go in different direction, that being Entity Construction Kit, "ECK."
One way of building with ECK is that you have "slices" which are entities that contain bundles and can also reference other entities that have their own bundles. On the content creation side, you can leverage the Inline Entity Form and Inline Entity Form Preview modules to create a minimalistic interface for content creators. It took me a long time to wrap my head around all this and lots of trial and error.
Now that I feel like I have a good handle on this, I decided to record a video tour of what I have been building. It's still a work in progress but I think it's well enough along to give a little demo.