You can do this with a block template. So in your theme’s functions file, you could set it up using something like:
function yourprefix_register_page_block_template() {
$post_type_object = get_post_type_object( 'page' );
$post_type_object->template = array(
array( 'acf/hero' ), // may need to adjust this based on block name
);
}
add_action( 'init', 'yourprefix_register_page_block_template' );
You can also do it with JS, the link above for block templates goes into how.
