Dia membentuk tanah liat dengan acuan.

Dia is a third-person singular pronoun, and it can mean either he or she. Malay does not usually mark gender in pronouns the way English does.

So:

• dia = he, she, or sometimes that person, depending on context

You need context to know which one is meant.

Malay often leaves tense unmarked unless time needs to be made explicit. The sentence by itself does not force one tense the way English usually does.

So Dia membentuk tanah liat dengan acuan could mean:

• He/She shapes the clay with a mold
• He/She shaped the clay with a mold
• He/She is shaping the clay with a mold

Time is usually understood from:

• context
• time words such as semalam (yesterday), sekarang (now), nanti (later)

For example:

• Semalam dia membentuk tanah liat dengan acuan. = Yesterday he/she shaped the clay with a mold.
• Sekarang dia membentuk tanah liat dengan acuan. = Now he/she is shaping the clay with a mold.

Membentuk comes from the root bentuk, which means shape, form, or structure.

With the prefix mem-, it becomes a verb:

• bentuk = shape/form
• membentuk = to shape, to form, to mold

In this sentence, membentuk is an active transitive verb, meaning it takes a direct object:

• membentuk tanah liat = to shape clay

This meN- verb pattern is extremely common in Malay.

Because membentuk is the standard verb form in normal written Malay for to shape/form.

Compare:

• bentuk = root word, often a noun or base form
• membentuk = the full active verb to shape

In casual speech, Malaysians may sometimes drop prefixes, but in standard Malay, membentuk is the expected form here.

Tanah liat is the normal Malay expression for clay.

The parts are:

• tanah = soil, earth, land
• liat = sticky, tough, clay-like

Together, tanah liat means clay. It is best learned as a set phrase rather than translated word-for-word every time.

So even though it has two words, it functions like one vocabulary item:

• tanah liat = clay

Here dengan introduces the instrument used to do the action.

So:

• dengan acuan = with a mold
• also naturally understood as using a mold

In many sentences, dengan can mean:

• with
• using
• by means of

In this sentence, with / using is the best sense.

Acuan usually means mold or mould—something used to give material a certain shape.

Depending on context, it can also mean:

• cast
• template
• pattern
• model

But in Dia membentuk tanah liat dengan acuan, the most natural meaning is a mold used to shape the clay.

Malay does not usually use articles the way English does. There is no direct equivalent that must appear before nouns in ordinary sentences.

So:

• tanah liat can mean clay, the clay, or some clay
• acuan can mean a mold, the mold, or mold

The exact meaning depends on context.

If Malay speakers want to be more specific, they can add other words, for example:

• acuan itu = that/the mold
• satu acuan = one/a mold

The sentence follows the common Malay order:

• Dia = subject
• membentuk = verb
• tanah liat = object
• dengan acuan = prepositional phrase

So the pattern is:

Subject + Verb + Object + Prepositional phrase

That is very similar to English:

• He/She shapes clay with a mold

In normal reading, dengan acuan describes how the shaping is done, so it attaches to the verb:

• membentuk ... dengan acuan = shape ... with a mold

So the meaning is:

• the person is using a mold to shape the clay

It would not normally be understood as describing a special kind of clay.

Yes. That is a very natural alternative.

• dengan acuan = with a mold
• menggunakan acuan = using a mold

The version with menggunakan is a bit more explicit about the idea of using a tool.

So both are good:

• Dia membentuk tanah liat dengan acuan.
• Dia membentuk tanah liat menggunakan acuan.

It can include both. Membentuk is a general verb meaning to shape / form / mold something into a form.

So it works for:

• shaping by hand
• shaping with a tool
• shaping with a mold

That is why membentuk ... dengan acuan sounds perfectly natural.

You could add a demonstrative such as itu or ini after the noun phrase.

For example:

• Dia membentuk tanah liat itu dengan acuan. = He/She shapes that/the clay with a mold.
• Dia membentuk tanah liat ini dengan acuan. = He/She shapes this clay with a mold.

Malay often marks definiteness this way rather than with an article like the.

Yes. Malay uses passives quite often.

A passive version could be:

• Tanah liat dibentuk olehnya dengan acuan.

This means:

• The clay is shaped by him/her with a mold.

In everyday Malay, oleh may be omitted in some contexts, but the active sentence you were given is the most straightforward form for a learner.