La lastra deve essiccare senza deformarsi.

La is the feminine singular definite article, meaning the.

• lastra is a feminine singular noun
• so it takes la
• la lastra = the slab / the sheet / the plate, depending on context

This is a very common pattern in Italian:

• il libro = the book
• la porta = the door

Lastra usually means a slab, sheet, plate, or pane, depending on the material and context.

For example, it can refer to:

• a slab of stone
• a sheet of metal
• a plate or panel
• sometimes a glass pane or similar flat object

So the best English translation depends on what kind of object is being discussed.

Because dovere is a modal verb, like must, have to, or should in English.

Here:

• deve = must / has to
• essiccare = to dry

So:

• deve essiccare = must dry / has to dry

This is the normal Italian structure:

• conjugated modal verb + infinitive

Other examples:

• deve partire = he/she must leave
• può entrare = he/she can enter
• vuole dormire = he/she wants to sleep

Deve is the third person singular present tense of dovere.

That form is used because the subject is la lastra, which is singular:

• io devo = I must
• tu devi = you must
• lui/lei deve = he/she must
• la lastra deve = the slab must

Even though lastra is a thing, Italian still uses the same third person singular verb form.

Both can relate to drying, but they are not always identical.

• asciugare often means to dry in a general sense, or to make dry
• essiccare usually sounds more like to dry out, to desiccate, or to become thoroughly dry, often in a more technical, industrial, or formal context

In a sentence like this, essiccare suggests a process of drying that matters materially or technically, not just wiping something dry.

So la lastra deve essiccare sounds more specialized than la lastra deve asciugare.

Because after a modal verb like dovere, Italian normally uses the infinitive.

So:

• deve essiccare not
• deve essicca

This is just like English:

• must dry not
• must dries

The conjugated verb is deve, and essiccare stays in its base form.

Senza means without.

So:

• senza deformarsi = without deforming / without becoming deformed / without warping

It introduces something that must not happen while the slab dries.

Other examples:

• senza parlare = without speaking
• senza vedere = without seeing
• senza problemi = without problems

Because deformarsi means to become deformed / to warp / to deform itself, while deformare usually means to deform something else.

Compare:

• deformare = to deform something
• deformarsi = to become deformed

In this sentence, the slab is not deforming another object. The slab itself must avoid changing shape. So the reflexive form is the natural one.

The -si is the reflexive pronoun attached to the infinitive.

It means the action happens to the subject itself.

So:

• deformarsi = to deform itself / to become deformed
• lavarsi = to wash oneself
• muoversi = to move oneself / to move

In this sentence, -si refers back to la lastra.

In Italian, with an infinitive, the reflexive pronoun is very often attached to the end of the verb:

• deformarsi
• asciugarsi
• muoversi

That is the normal dictionary form of reflexive infinitives.

With a conjugated verb, the pronoun usually comes before the verb:

• si deforma = it becomes deformed
• si muove = it moves

So here:

• senza deformarsi is correct because the verb is an infinitive

Yes. La lastra deve essiccare senza deformarsi and La lastra deve essiccare senza che si deformi are both possible, but they are not identical in style.

• senza deformarsi is more compact and common in technical or neutral writing
• senza che si deformi is a fuller clause and can sound a bit more explicit

Both mean essentially:

• the slab must dry without becoming deformed

The infinitive version is very natural here.

Here it is being used intransitively.

That means the slab itself undergoes the drying process:

• la lastra deve essiccare = the slab must dry

But essiccare can also be used transitively in some contexts:

• essiccare qualcosa = to dry something out

So the verb can work both ways depending on meaning and context.

The sentence breaks down like this:

• La lastra = the subject
• deve = modal verb, present tense
• essiccare = main infinitive verb
• senza deformarsi = adverbial phrase explaining the condition

So literally it is something like:

• The slab must dry without deforming itself

More natural English might be:

• The slab must dry without warping
• The slab must dry without becoming deformed

Yes, it sounds fairly technical, procedural, or instructional.

Reasons:

• lastra is a material/object word
• essiccare sounds more technical than everyday asciugare
• senza deformarsi describes a material requirement or process condition

This is the kind of sentence you might see in:

• manufacturing instructions
• materials science
• industrial processes
• product handling guidelines