The theme I am using is on my test WordPress site is the Atomic Blocks theme from Array Themes. There is a version of the theme in the WordPress repository, but the version I am using is direct from Array Themes because I have a subscription. I am not sure what if any differences there are between the two versions. I am also using the Atomic Blocks Gutenberg plugin, which is also built by the people at Array Themes. It supplements the standard Gutenberg blocks to help you build pages. It is freely available from the Atomic Blocks site. I am taking things slowly, using Gutenberg to get familiar with it. Note: One of the advantages of using container blocks is that although one might write paragraphs of text as separate blocks, one can contain them within one larger block and so, for example, I am able to put a background colour around all of the blocks rather than have them as separate blocks with white space showing between the paragraphs.