L’engobe et la barbotine décorent la plaque de terre.

In French, le and la usually shorten to l’ before a vowel sound or a silent h. This is called elision.

So:

• le engobe → l’engobe

Here, l’ stands for le, because engobe is a masculine noun.

You have to know the gender of the noun.

• engobe is masculine → le engobe → l’engobe
• barbotine is feminine → la barbotine

Because l’ can represent either le or la, the noun’s gender tells you which one it is.

French usually keeps the article before each noun in a list or pair of nouns.

So French says:

• l’engobe et la barbotine

rather than dropping the second article.

This is very normal in French. English sometimes omits repeated articles more freely, but French often repeats them.

Because the subject has two parts:

• l’engobe
• la barbotine

Together, they make a plural subject, so the verb must also be plural.

That is why French uses:

• décorent = decorate / are decorating

Compare:

• L’engobe décore la plaque. = The engobe decorates the slab.
• L’engobe et la barbotine décorent la plaque. = The engobe and the slip decorate the slab.

Because it is the third-person plural form of the verb décorer in the present tense.

Present tense:

• je décore
• tu décores
• il / elle décore
• nous décorons
• vous décorez
• ils / elles décorent

Since the subject is plural, French uses ils/elles décorent.

A useful thing to know: in normal speech, the -ent at the end is usually not pronounced.

The accent is part of the spelling of the verb décorer.

You will see:

• décorer
• je décore
• ils décorent

The é shows a closed ay-like sound. French accents are not optional decoration; they are part of correct spelling.

Here de terre works like of clay / of earth or made of clay. In this kind of material phrase, French often uses de + noun without an article.

So:

• une plaque de terre = a clay slab / slab of clay

If you said de la terre, it would more strongly suggest some earth/soil as a separate mass noun, not the set expression describing the object’s material in the same way.

Sometimes en terre is possible, but it is not exactly the same in feel.

Very roughly:

• de terre often identifies the material in a direct, noun-linked way
• en terre often means made of clay/earthenware

In a ceramics context, plaque de terre is very natural for a clay slab.
So the original sentence sounds appropriate.

A simple approximation is:

lan-gob ay la bar-bo-teen day-cor la plak duh tair

A few helpful points:

• l’engobe: the l’ links straight into the next word
• et is usually pronounced ay
• barbotine sounds roughly like bar-bo-teen
• décorent: the final -ent is usually silent
• terre sounds like tair

So décorent is pronounced roughly like day-cor, not day-cor-ent.

It follows the same basic pattern as English:

subject + verb + object

• L’engobe et la barbotine = subject
• décorent = verb
• la plaque de terre = object

So this sentence is structurally quite straightforward for an English speaker. The main challenges are the articles, noun gender, and the plural verb form.