Getting 4 stars here is quite tough. You really need to balance the workload between chefs. The first 5 dishes are the same (for single players), so you can exactly follow what I do here.
The rafts align either vertically or horizontally, with drifting in transition. You can find out when the rafts starts to drift apart by checking the surroundings. For vertical alignment, the rafts starts to drift apart when you see quite a large tree that follows a bunch of wooden pillars. Be careful when sending completed dishes though, because you may tend to throw it into the trash bin instead. For horizontal alignment, the rafts start to drift as soon as passing a small island with tree.
During these alignments, you must always pass dirty plates so that the side with deep fryer always have clean plates. Meanwhile, send empty plates when you are planning to serve salad, because cut (uncooked) ingredients can always be thrown between rafts. Make sure that both chefs are cutting ingredients at all times.
Just keep practicing this level. It is quite tough. This gamplay suggests 14 servings to get 4 stars, but in reality, it depends on how often salads/fritters pop up. If fritters pop up more often, then you may need less servings.
Hope you enjoy this video, stay tuned for more gameplay!
Mister Fudo signing off!