Add archive slug to default post post type

Using the permalink settings to configure your post permalinks, then modifying the author permalinks seems like the way to go.

I set up the permalink rules like this:

/post/%postname%/

Then used this code to modify the author permalinks (source):

// change base of author pages- need to save permalinks to take effect
function wpse82004_change_author_permalink(){
    global $wp_rewrite;
    $wp_rewrite->author_base="author";
    $wp_rewrite->author_structure="https://wordpress.stackexchange.com/" . $wp_rewrite->author_base . '/%author%';
}
add_action( 'init','wpse82004_change_author_permalink' );

Remember to save permalinks afterwards.