Hey heohni,
you should define a Route in the routes.php for your needs like:
Router::connect(
'/my-custom-rote/whatever-i-want/:id/:slug/:etc',
['plugin' => 'MyPlugin', 'controller' => 'TheController', 'action' => 'TheAction']
);
Its very simple - or read the docs https://book.cakephp.org/3.0/en/development/routing.html#quick-tour