Unsuk Chin is her Piano Etude No. 2 (Sequenzen) from “12 Piano Etudes” starts with a slow motif using notes in the low register of the piano.
She started with the material she wanted to use in a fast way. She started im a slow way and then accelerated until reach the fastest she wanted.
I will take this as a reflection that I want to make the opposite - at the moment I have a fast material and I want to transform that into a slow material. In as way, I need to understand what is the slow version of my material - everything I have sketched so far.
In a way what you need to do is translate your first movement material into a slow way of expressing it.