yangpareul yalbge sseoreoseo saelleodeue neoheoyo.

Korean often omits the subject when it is obvious from context.

In a recipe or cooking instruction, the understood subject is usually:

• you if someone is giving instructions, or
• a general one / the cook

So even without a subject, the sentence sounds completely natural.

를 is the object marker.

Here, 양파를 means the onion is the thing being acted on. In this sentence, the onion is what gets:

• sliced first, and then
• added to the salad

So 양파를 marks onion as the direct object.

얇게 is the adverb form of 얇다 (to be thin).

The ending -게 turns many Korean descriptive verbs/adjectives into adverbs:

• 얇다 → 얇게 = thinly
• 빠르다 → 빠르게 = quickly
• 작다 → 작게 = smallly / in a small way depending on context

So 얇게 썰어서 means slice it thinly.

Because 얇게 describes how you slice, not what kind of onion it is.

• 얇게 썰다 = to slice thinly
• 얇은 양파 = a thin onion

In this sentence, the important idea is the manner of cutting, so the adverb 얇게 is used.

썰다 usually means to slice or cut up food with a knife.

It is very common for ingredients like:

• onions
• carrots
• meat
• cucumbers

자르다 is a more general to cut.

So:

• 썰다 = slice/chop ingredients
• 자르다 = cut in a broader sense

In cooking, 썰다 is often the more natural choice.

Here -어서 connects two actions:

1. 썰다 = slice
2. 넣다 = put in / add

So 썰어서 means something like:

• slice it and then...
• after slicing it...

In this sentence, it shows sequence: first slice the onion thinly, then put it into the salad.

Here it is showing sequence, not reason.

-아/어서 can sometimes mean because, but in this sentence it means:

• do action 1, then do action 2

So 썰어서 샐러드에 넣어요 means:

• slice it, then add it to the salad

not

• because you slice it, you add it to the salad

Because 에 marks the place/destination where something goes.

With 넣다 (to put in / insert / add), Korean often uses:

• A를 B에 넣다
• put A into B

So here:

• the thing being added is the onion
• the destination/container is the salad

That is why 샐러드에 means into the salad.

Because Korean often omits repeated objects when they are already clear.

A fuller version could be:

• 양파를 얇게 썰어서 샐러드에 양파를 넣어요

But that sounds repetitive. Once 양파 has already been mentioned, Korean naturally leaves it out the second time.

English often keeps it with it:

• Slice the onion thinly and add it to the salad.

Korean usually just omits it.

In Korean, the present polite form is often used for:

• everyday statements
• instructions
• recipe steps
• demonstrations

So 넣어요 can mean:

• I put it in
• you put it in
• put it in in an instructional style

In recipes, this style sounds natural and common. It is polite, clear, and not too harsh.

Yes, 썰고 샐러드에 넣어요 is also possible.

The difference is small, but often:

• -고 = simple and
• -어서 = and then / after doing that, with a slightly tighter connection

In cooking instructions, -어서 often feels very natural because one action directly leads to the next.

So both can work, but 썰어서 nicely emphasizes the sequence.

A useful way to break it down is:

• 양파를 = onion + object marker
• 얇게 = thinly
• 썰어서 = slice and then / after slicing
• 샐러드에 = into the salad
• 넣어요 = put in / add

So the structure is basically:

• [object] + [how] + [verb 1 + connector] + [destination] + [verb 2]

This is a very common Korean pattern for step-by-step actions.