This is an excellent question! “Dont” is used here because it complements “façon”, and it would be “in which” in English. “Avec laquelle” is wrong because this is “de quelle façon”. Saying “cela dépend de la façon DE laquelle l’employé négocie...” is correct, but rarely used. De quelle façon l’employé négocie-t-il? L’employé négocie de la façon qu’il veut. :) La façon dont l’employé négocie est celle qu’il veut. We negotiate WITH someone IN a (certain) way. How/In which way does the employee negotiate? The employee negotiate in the way that he wants. The way in which the employee negotiates is the way that he wants. It is all about nuances; let’s have a look at these two sentences: C’est la moto avec laquelle je me déplace. This is the motorbike with which I travel. C’est la voiture avec laquelle/dans laquelle je me déplace. This is the car with which/in which I travel. Here, “dont” is not used, but note that with “voiture”, we can either say “avec laquelle” or “dans laquelle”. In certain cases, it depends on the context whether one is correct or not or whether both are correct. In your sentence, “dont” and “de laquelle” are correct. I hope that helps.