1) Fantasy needs a structure in any case: absurd stories must be realistic stories first of all.
2) You might take three words at chance and build any story with them.
3) Be inspired from your favourite subject. Omouamua?
4) My favourite learning method: imagine you are going to start your business there, imagine you are talking with your customers. Any word you know in that language can turn out useful.
7) Above all, there is only one rule: doing.
I hope it helps