La cuisson biscuit se tient dans le four.

Because cuisson is a feminine noun in French, so it takes la.

• la cuisson = the cooking / baking / firing
• not le cuisson

This is something you usually just have to learn with the noun.

In a ceramics context, cuisson biscuit is a technical expression. It refers to the first firing of clay objects, often called bisque firing in English.

So here biscuit does not mean an English-style biscuit or cookie. It is a specialized word used in pottery and ceramics.

Outside that technical context, many learners would expect biscuit to mean a food item, which is why this phrase can look confusing at first.

That is a very reasonable question, because in many ordinary French phrases you would expect de:

• la cuisson du pain
• la cuisson du gâteau
• la cuisson du biscuit

But cuisson biscuit is a specialized compound expression used in ceramics. In technical vocabulary, French sometimes puts two nouns together without de, especially in set phrases.

So:

• cuisson biscuit = a fixed technical term
• cuisson du biscuit = would sound more like the cooking of a biscuit as food

Here se tient means takes place or is held.

So:

• La cuisson biscuit se tient dans le four. = The bisque firing takes place in the kiln/oven.

This use of se tenir is common for events, activities, or processes:

• La réunion se tient à 14 heures.
• Le festival se tient en juin.

In this sentence, it is being used for the firing process.

Because se tenir and tenir are not the same.

• tenir often means to hold
• se tenir can mean to take place, to be held, to stand, or to keep oneself in a certain position, depending on context

So this is not a literal reflexive meaning like holds itself. It is just the normal French verb form for this expression.

Both dans le four and au four can exist in French, but they are used a little differently.

Here, dans le four emphasizes that the process happens inside the oven or kiln.

• dans le four = inside the oven/kiln

By contrast, au four is often used with verbs like:

• mettre au four = put in the oven
• cuire au four = bake in the oven

So in this sentence, dans le four makes sense because the firing is physically taking place inside it.

It depends on the context.

• In everyday cooking, four usually means oven
• In ceramics or pottery, four can mean kiln

Since cuisson biscuit is a ceramics term, four here would most naturally be understood as kiln.

It is understandable, especially in a specialized ceramics context, but it sounds a bit technical and not very everyday.

A more ordinary or more broadly natural phrasing might be:

• La cuisson biscuit se fait dans le four.
• La cuisson du biscuit se fait dans le four. (if talking about food, not ceramics)
• Le biscuit cuit dans le four. (for an ordinary food meaning)

So the original sentence works best if it is clearly part of pottery/ceramics vocabulary.

It is the present tense, third person singular, of se tenir.

• je me tiens
• tu te tiens
• il / elle / on se tient

Here the subject is La cuisson biscuit, which is singular, so French uses se tient.

The present tense is often used in French for general truths, descriptions, or standard processes, which fits this sentence well.

In French, biscuit is pronounced roughly like bees-kwee.

A few important points:

• the final t is silent
• the ui sound is not like English oo-ee exactly; it is a French sound, but kwee is a useful approximation

So it is very different from the English pronunciation of biscuit.