Not sure if meta box can achieve this - but I will try you anyway!
I would like to autogenerate a featured image, and so when the post is shared on socials - then there is a featured image.
I would like to create the featured image by creating a template, which combines the author avatar and a custom post field.
I would like this to be triggered when the post is published.
Do you know how I could do this using metabox?