Learn Spanish (Latin America): La forma en que usas la coctelera mejora el cóctel. - The way you use the cocktail shaker improves the cocktail.

We use the indicative usas because the speaker is talking about a known, established reality. They have already seen or experienced how you currently use the cocktail shaker. If they were giving instructions for a hypothetical future situation (like 'the way you might use it later'), they would use the subjunctive uses.

Could I say la forma en la que instead of just la forma en que?

Yes, absolutely! With la forma, la manera, and el modo, you can optionally include the definite article (el or la) before que. Both la forma en que and la forma en la que mean the exact same thing and are widely used by native speakers.

Why do we use the preposition en before que in this sentence?

In English, we often just say 'the way that' or skip the joining word entirely ('the way you use'). But in Spanish, the structures la forma, la manera, and el modo require the preposition en to link them to the clause, expressing 'in the way that'. Dropping it to say la forma que usas sounds incomplete to a native speaker.

Why isn't mejora used reflexively here as se mejora?