Mi abuela prefiere el romero al tomillo, pero siempre quita el laurel antes de servir.

Because a + el contracts to al. This is a standard rule in Spanish.

So:

• a el tomillo → al tomillo

Also, the verb preferir normally uses the pattern preferir X a Y = to prefer X to Y. That is why the sentence says prefiere el romero al tomillo.

With preferir, Spanish compares one thing to another using a:

• Prefiero el café al té = I prefer coffee to tea
• Prefiere el romero al tomillo = She prefers rosemary to thyme

So here a is part of the normal grammar of preferir when you say what is preferred over something else.

Yes. Preferir is an e → ie stem-changing verb in the present tense, except in the nosotros and vosotros forms.

Present tense:

• yo prefiero
• tú prefieres
• él/ella prefiere
• nosotros preferimos
• vosotros preferís
• ellos/ellas prefieren

So prefiere is the correct form for mi abuela.

Both verbs can relate to removing something, but quitar is very natural for taking away / removing an ingredient from a dish. In cooking, quitar el laurel sounds very normal: you put in the bay leaf for flavour, then remove it before serving.

Sacar usually focuses more on taking something out from inside somewhere. It is possible in some contexts, but quitar fits this sentence very well.

Because the full direct object is already stated: el laurel. Spanish does not need a pronoun if the noun is right there.

• Quita el laurel = She removes the bay leaf
• Lo quita = She removes it

Both are grammatical, but if you already name the thing, the pronoun is not necessary.

After antes de, Spanish uses an infinitive when talking about an action in a general way, especially when the subject is the same or understood.

• antes de servir = before serving

If Spanish needs a new subject and a full clause, it usually uses antes de que + subjunctive:

• antes de que lleguen = before they arrive

So antes de servir is exactly the normal structure here.

It is understood from the context, so Spanish leaves it unstated. In a cooking sentence like this, servir usually means serve the food / serve the dish / serve the meal.

Spanish often omits objects when they are obvious:

• Ya comí = I already ate
• Sirve primero = Serve first

So antes de servir sounds complete even without saying exactly what is being served.

Spanish adverbs like siempre are quite flexible, but putting siempre before the verb is very common and natural:

• siempre quita el laurel

You could also hear quita siempre el laurel, but that can sound a little more marked or emphatic depending on context. The version in the sentence is the most neutral one.

The present tense in Spanish is often used for habits and repeated actions, just like in English:

• Mi abuela prefiere...
• siempre quita...

This tells us what she generally does, not just what she is doing right now. It is a habitual present.

Not necessarily. In Spanish, el laurel can refer to bay as an ingredient in a general sense, not only to one literal leaf. In cooking, though, it often does suggest the bay leaf that was added to the dish and then removed.

If you wanted to be very explicit about multiple leaves, you could say las hojas de laurel.

Yes, you should learn them with their articles:

• el romero
• el tomillo
• el laurel

All three are masculine. Since these nouns do not all have obvious endings that clearly show gender, learning the article together with the noun is the safest habit.

A rough guide for Spain:

• romero ≈ ro-MEH-ro
• tomillo ≈ to-MEE-yo
• laurel ≈ lau-REL
• servir ≈ ser-BEER in standard Castilian pronunciation, with the v/b sound being the same in Spanish

A few useful notes:

• The r in romero is tapped.
• ll in tomillo is usually pronounced like y in most of Spain.
• The j sound does not appear here, so there is nothing especially harsh to pronounce in this sentence.