Sometimes you just need to output some posts based on the post you are already on. You could place this code on your single post template and it would return 3 posts based on the categories said post are associated with. The
'post__not_in' => array(get_the_ID()), line ensures the post you are currently on doesn’t show in this list. You could also replace
'category__in' => wp_get_post_categories(get_the_ID()), with
'tag__in' => wp_get_post_tags(get_the_ID()), to base this query off Tags instead of Categories.
I am hoping in the near future this is something that can be achieved with the Full Site Editor and the Query block.