の details

write + の — turns a verb or a whole clause into a noun

kaku no

の — turns a verb or a whole clause into a noun

meaning: writing

私わたし、朝あさ早はやく起きるおきるのが苦手にがてなんだ。

watashi, asa hayaku okiru no ga nigate na n da.

I'm bad at getting up early. casual

隣となりの部屋へやで誰だれかが笑わらっているのが聞きこえた。

tonari no heya de dareka ga waratte iru no ga kikoeta.

I heard someone laughing in the room next door. neutral

Examples

makes a noun of the action or state, so が・を・は can take it

私わたし、朝あさ早はやく起おきるのが苦手にがてなんだ。

watashi, asa hayaku okiruno ga nigate na n da.

I'm bad at getting up early. casual

毎朝まいあさ走はしるのは、思おもったより楽たのしいです。

maiasa hashiru no wa, omotta yori tanoshii desu.

Running every morning is more fun than I expected. neutral

昨日きのうは薬くすりを飲のむのをすっかり忘わすれていた。

kinou wa kusuri o nomu no o sukkari wasurete ita.

Yesterday I completely forgot to take my medicine. neutral

the event as witnessed — after 見[み]える・聞[き]こえる・見[み]かける and the other perception verbs, こと is not available

隣となりの部屋へやで誰だれかが笑わらっているのが聞きこえた。

tonari no heya de dareka ga waratte iru no ga kikoeta.

I heard someone laughing in the room next door. neutral

先さきほど、部長ぶちょうが会議室かいぎしつを出でられるのをお見みかけしました。

sakihodo, buchou ga kaigishitsu o derareru no o o mikake shimashita.

I saw the manager leaving the meeting room a little while ago. formal

Where the nominalized clause is itself the predicate (AはBだ), こと takes
over — 趣味しゅみは泳およぐことです, since 〜のです would be read as the
explanatory ん／の instead.

こと
Two nominalizers for one job, split by how the speaker knows the event — の is the spoken default and is the only option when the clause is seen, heard or interrupted in progress (見みえる・聞きこえる・止とめる), while こと is the written pick and the only one the set frames ことができる／ことがある accept.

の
What follows decides — the nominalizer hands its clause to a particle and a predicate (泳およぐのが好すきだ), while sentence-final の closes the utterance and nothing but a final particle or intonation follows it (どうしたの・知しらないのよ).
の
What precedes decides — the genitive links two words that were nouns already (会社かいしゃの車くるま), the nominalizer takes a whole clause and manufactures a noun out of it (毎朝まいあさ走はしるの).
んです
The ん of んです is this の contracted, but it explains a finished sentence instead of nominalizing one — the test is what comes next: of the two, only the nominalizer feeds a case particle (のが・のを), while explanatory ん runs into だ／です, and on into んですが・んでしょう.

のが好き
〜のが好すきだ is this の plus an adjective that can only take a が-subject, so the clause must become a noun first; ことが好すきだ is grammatical but reads like a questionnaire item next to it.