Select the default shipping option

We always ship every Bol order that comes into Woo using a fixed method, namely "PostNL Letter Mail." For each order, we currently have to select this from all the available shipping options (in fact, unfortunately, we even have to do this for each item within every order). We would like to add a default shipping option (which can be overridden in very rare cases if necessary). That would be very helpful and save a lot of work.