What I meant was that, write something totally your own. Write whatever you want to. If you want to limit yourself to classical harmony rules than do so, if not than be crazy and write whatever chord you want. I said take Prelude 1 as a model by means of one chord per measure.
This is going to be easy, I don't want you to finish a composition right now, just write progression as if it is an accompaniment to something. Think of it as the basis of your soon-to-be composition. If you get stuck, look what Bach did, how did he keep the flow, with modulations ? pedal tones ?
ok. just go and write something now !
)))
EDIT: remember, only potatoes! ..