To write on something random, it means that there are no preconceived notions of what it’ll be about. In order for this to be effective (and productive), a routine of writing had to be in order.
It’s kind of like journal writing. Journal writing is about being spontaneous–letting the ideas flow without hinderance, such as pausing to edit. Whereas journaling draws inspiration from one’s own experience, writing an essay, story, or a reflection piece draws its inspiration from the strength of an idea itself. If the random idea(s) is inspirational, it can take a writer down many pages of written words.
When someone gets in to the habit of writing, the ideas will flow off their fingertips, even if they’re not sure what to write about or what the end result will be. They can write as if they were free-styling or playing a musical instrument. In those cases, the words or the notes flow based on feeling and rhythm. The same can happen with writing. It’s as if the thoughts are building up to a crescendo. Afterward, the words take them where the work needs to go.
Fallton Havenstonne 