@stinkykong Although you seem to have resolved it using Atomic Blocks, I was facing the same problem and wanted to do it using the Gutenberg editor only. So I figured out a ‘hack’ that worked for me on both front-end and back-end. My requirements were slightly different in that I needed to wrap a couple of blocks in a single column so that I could make all those blocks have the same background colour and appear as a different section on the page.
Insert a block of “custom HTML” before your “section” (ie, before your collection of blocks that you want to put in one column) and put an opening div in it like so:
<div class="your-custom-class">
If you’ve not guessed it already, insert another custom HTML block after your “section” and put a closing div tag in it:
</div>
Now you can add any CSS to that custom class you added through the custom CSS option in Customise view, and voila you have a section of blocks!
