Collocations can be fixed, where it is difficult to replace one of the words with an alternative, or freer, allowing for more choice of words.
Example
'Utter disaster' is a fixed collocation, as there are few words that can be used instead of 'disaster'. 'Make a cake' is a freer collocation, as there are many words that can be used instead of 'cake'.
In the classroom
Collocations often have to be memorised; teachers can help learners focus on and remember collocations by exposing them to authentic texts, and by helping students to record collocations in their notebooks.
Further links:
https://www.teachingenglish.org.uk/article/collocation-pelmanism
https://www.teachingenglish.org.uk/article/lexical-exploitation-texts