You can use the activation hook and call function wp_insert_post()
class MyPlugin {
static function install() {
$my_post = [
'post_title' => 'My page title',
'post_content' => 'My page content',
'post_status' => 'publish',
'post_author' => 1, // Set author id here
'post_type' => 'page',
];
wp_insert_post( $my_post );
}
}
register_activation_hook( __FILE__, [ 'MyPlugin', 'install' ] );