I see many posts on this forum which seem to be very readable posts of an entire notebook. This excellent post is a good example. I have been posting by entering code a piece at a time, interleaved with commentary.
How are these whole notebook posts made?
Check the toolbar
Yes, embedding a notebook in a post is a very efficient way to share your ideas. Steps are the following:-
keep settings as they are, click Publish red button
and copy the published link
Now create your post and use the button "Add Notebook" Rohit showed in his reply, and copy the url, check the backup box, and click add notebook.
Thank you Rohit and Ahmed for the nice instructions.