The Newspaper theme allows you to include flex blocks inside your content using a Single Post Template.
Click on the single post content element and click on the Ads tab. Here, you can add the code for the flex block to display inside the post content. You can find an example of code to add a flex block with a random post here.
Example: Flex block with a random post. The sample code added in the field for the article inline ad 1.
To make your inline blocks, create a new page and set the flex block that you want to use; after you edit it, copy the shortcode for the flex block from the page and set it like in the above example. On the block, you can change different filters.
The code is the one set between the “vc_column” and “/vc_column” shortcodes.