This challenge is all about anticipation, so my expectation was that the job would be done quickly.
Just a small animation.
Well it took a bit longer 
In previous lesson we’ve learned to use the Grease Pencil, to sketch some steps of the animation. I did this and came to the conclusion, it will be a large project.
So what I did was creating 18 or so Blender mini animation projects. Each of 20 - 50 frames.
Whereby most of the animations had the same default start and end position of the Cube (standing in the middle).
I rendered the animations as .PNG frames. I created about 600 unique frames. Sometimes I re-animated some projects, for smoother animations. Or because of change in the story.
All these animation sequences I imported into Blender and composed the animation. Sometimes duplicating an animation. Resulting in the displayed animation (no sound).
Lessons learned:
- Control bones are handy, but think in advance what kind of animation you need. And build the armature accordingly. For example I had a control bone for the Cube bottom square. Never needed it.
- Stick to the plan, or create one.
- Keep you project small.
- Think about re-using animation.
- Think about re-using Armature animation. Don’t animate vertices or objects. Use Armature bones!
- Redo animations, if they don’t fit or feel odd.
Happy render times.