Пекарь сделал надрез на хлебе.

Because сделал is the perfective past form of сделать, and it presents the action as completed: the baker made the cut.

By contrast, делал is imperfective and would usually suggest an ongoing, repeated, or uncompleted action, such as was making or used to make.

So:

• Пекарь сделал надрез на хлебе. = the baker made a cut / finished making it
• Пекарь делал надрез на хлебе. = the baker was making a cut / used to make a cut

Сделал tells you several things at once:

• past tense
• perfective aspect
• masculine singular

In the Russian past tense, verbs agree in gender and number, not person.

So:

• сделал = masculine singular
• сделала = feminine singular
• сделало = neuter singular
• сделали = plural

In this sentence, сделал matches пекарь, which is grammatically masculine.

Пекарь is in the nominative case because it is the subject of the sentence — the person performing the action.

The basic question for the subject is who? / what?

• Кто сделал надрез? — Пекарь.

So пекарь stays in its dictionary form here.

Надрез is the direct object, so it is in the accusative case.

However, for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: надрез
• accusative: надрез

That is why there is no visible ending change here.

Russian often uses a light verb + noun structure, just like English does in phrases such as make a cut.

So сделать надрез means to make a cut / incision / slit.

A one-word verb is also possible in some contexts, for example надрезать. But сделать надрез is a very normal and natural expression. It can sound a bit more concrete or technical, depending on context.

Because на хлебе describes the location of the cut: it is on the bread.

With на, Russian often uses:

• accusative for motion toward / onto something
• prepositional for location on something

Compare:

• положить на стол = put onto the table
• лежать на столе = lie on the table

Here the cut is located on the loaf’s surface, so Russian uses на хлебе.

Хлебе is the prepositional singular of хлеб.

The noun хлеб is masculine, and in the prepositional singular it becomes:

• хлеб → на хлебе

So the ending -е marks the prepositional case here.

Because Russian normally treats this kind of cut or scoring as something made on the surface of the loaf, not deep inside it.

So:

• на хлебе = on the bread, on the loaf’s surface
• в хлебе = in the bread, inside the bread

For a baker scoring a loaf, на хлебе is the natural choice.

In this sentence, сделал is masculine, so it suggests either:

• the baker is male, or
• masculine wording is being used in a generic way

If the speaker clearly meant a female baker, you would very often see:

• Пекарь сделала надрез на хлебе.

So the verb form gives an important clue.

Russian has no articles, so it does not have direct equivalents of a/an and the.

That means Пекарь сделал надрез на хлебе could mean:

• The baker made a cut on the bread
• A baker made a cut on the bread
• sometimes even The baker made the cut on the bread

The exact meaning depends on context.

No, Russian word order is relatively flexible because the cases show the grammatical roles.

Пекарь сделал надрез на хлебе is a neutral, natural order.

But other orders are possible for emphasis, for example:

• Надрез на хлебе сделал пекарь. = It was the baker who made the cut on the bread.
• На хлебе пекарь сделал надрез. = On the bread, the baker made a cut.

So the default order is straightforward, but Russian can move things around to change focus or emphasis.