[Coda]

Oh!

Those aren't two-kana particles. Those are separate one-kana particles!

The easier one to explain is の. When used after a verb, it turns the verb into a gerund (that is, a noun). In English, this is using the -ing form of a verb as a noun. So for example, you might say 走るのが好き (hashiru no ga suki, "I like running") or 働くのが難しい (hataraku no ga muzukashii, "working is difficult").

か when used in that context could be translated as "whether" or "if". So 行くのか知らない (to use the example in your link) means "I don't know if I'm going." (You might see 行くかどうか which would be "whether I'm going or not".)

は in this case is just the same old wa you've always seen. It's being used in the contrastive sense here.