Templates can be declared in JS or in PHP as an array of blockTypes (block name and optional attributes).
The first example in PHP creates a template for posts that includes an image block to start, you can add as many or as few blocks to your template as needed.
PHP example:
<?php
function myplugin_register_template() {
$post_type_object = get_post_type_object( ‘post’ );
$post_type_object->template = array(
array( ‘core/image’ ),
);
}
add_action( ‘init’, ‘myplugin_register_template’ );
