Я отрезал ещё один ломтик батона и сделал бутерброд с ветчиной.

Отрезал is a perfective verb, so it presents the action as a completed whole: he/I cut off a slice.

• резал = was cutting / cut repeatedly / cut in a general sense
• отрезал = cut off, successfully separated

In this sentence, the speaker means that one slice was cut off and then a sandwich was made, so the completed action is what matters.

Because ломтик usually takes the thing-sliced in the genitive case.

So:

• ломтик хлеба = a slice of bread
• ломтик сыра = a slice of cheese
• ломтик батона = a slice of a loaf / bread roll loaf

Here, батона is the genitive singular of батон.

Here ещё means another or one more.

So:

• ещё один ломтик = one more slice / another slice

This is a very common use of ещё with numbers:

• ещё одну чашку = one more cup
• ещё два дня = two more days

By itself, ещё can also mean still or yet, but in this sentence it clearly means one more.

Один literally means one, but with ещё it often helps express another very naturally.

• ещё ломтик = some more slice / another slice, but less specific
• ещё один ломтик = one more slice, exactly one additional slice

So ещё один is the standard way to say another in many contexts.

Батон in Russian usually means a long loaf of white bread, not the English word baton.

It is a specific kind of bread word, different from the broader хлеб.

For example:

• хлеб = bread in general
• батон = a loaf, especially a white bread loaf
• булка can also mean a bread roll or bun, depending on context

So ломтик батона is more specific than just a slice of bread.

Because the preposition с in the meaning with normally takes the instrumental case.

• ветчина = nominative
• ветчиной = instrumental

So:

• бутерброд с ветчиной = a ham sandwich
• чай с сахаром = tea with sugar
• с сыром = with cheese

This is one of the most common uses of the instrumental case.

Not always exactly.

In Russian, бутерброд often means a piece of bread with something on it, including an open-faced sandwich, which is very common in Russian usage.

Depending on context, it can also refer more generally to a sandwich. So in translation, sandwich is often fine, but culturally the Russian word can be a little broader or different from the English image of two slices of bread.

Russian commonly says сделать бутерброд = to make a sandwich.

This is perfectly natural.

Other verbs are also possible in some contexts, such as:

• приготовил бутерброд = prepared a sandwich
• собрал бутерброд = assembled a sandwich

But сделал бутерброд is simple, standard, and idiomatic.

That is the marker of the past tense in Russian.

In the singular past tense, Russian verbs also agree with gender:

• отрезал, сделал = masculine
• отрезала, сделала = feminine
• отрезало, сделало = neuter

Since the speaker is Я, this tells you the speaker is male. If the speaker were female, it would be:

Я отрезала ещё один ломтик батона и сделала бутерброд с ветчиной.

Yes, Russian often can omit the subject pronoun if it is clear from context.

So you could say:

Отрезал ещё один ломтик батона и сделал бутерброд с ветчиной.

That can sound natural in the right context, especially in conversation or narrative. But including Я is also completely fine, especially if you want to be explicit or contrast yourself with someone else.

Yes. Russian word order is fairly flexible, because case endings show grammatical relationships.

The neutral order here is:

Я отрезал ещё один ломтик батона и сделал бутерброд с ветчиной.

But other orders are possible for emphasis, for example:

• Ещё один ломтик батона я отрезал и сделал бутерброд с ветчиной.
• Я сделал бутерброд с ветчиной и отрезал ещё один ломтик батона.
  This changes the sequence of events, so it is not the same meaning in context.

So yes, word order can move around, but it affects emphasis, focus, and sometimes even the implied order of actions.

Russian has no articles.

So nouns like ломтик, батона, and бутерброд appear without words corresponding to a/an/the. Whether something is definite or indefinite is understood from context.

For example:

• сделал бутерброд could mean made a sandwich or made the sandwich, depending on the situation.

In this sentence, English naturally uses a: made a ham sandwich, but Russian does not need a separate word for that.

Yes. Ломтик usually means a thin slice, while кусок means a piece or chunk, often less specifically.

So:

• ломтик батона = a slice of the loaf
• кусок батона = a piece of the loaf

Since bread for a sandwich is usually sliced, ломтик is the more natural choice here.