It's fun to read such a piece after I just did a similar thing, on a somewhat smaller scale. I just built my first custom block. It's a checklist block that my wife needed on her site, and existing ones didn't do what she needed. It was a pretty smooth experience. I used one of the examples from https://github.com/WordPress/gutenberg-examples as a starting point and they very helpful. So if anyone wants to get started quickly, check these out, they are well documented too. What worries me a bit however, is the size of my node_modules folder. I'm just creating a simple block, and it's 350MB! I wonder whether that is considered normal for a Webpack based setup these days?