For example, look at the phrase I don't know. Every time you say this, do you think about the tense and the conjugation of the auxiliary verb do? Probably you just say it, almost like it's one word, idunno. That is a chunk. Look at the photos on this page - each one has a phrase on it that we use to talk about the weather. These are chunks, and you can learn them as a set phrase.
This how our brain remembers a lot of our native language, so if you can replicate this in a foreign language, you will speak much more naturally.
If you look at the Jason Derulo song lyrics I posted the other day (by the way, the other day is a chunk and so is by the way), you can find some good chunks, like come along, take a sip, my deepest, darkest secret.
So my advice is to stop writing down one word at a time in your vocabulary notebook, and try to learn words that go together. And then use them of course.