Roam's Daily Notes are a good starting point for an incremental writing practice because unrelated ideas can exist in the same day and the user can review them together.
A prerequisite is to use Daily Notes as an idea inbox.
Every day, we can add the date as a one-sided review cards, e.g. July 30th, 2020, and use a spaced repetition software, like Anki, to review them.
During review, we go to the Daily Note corresponding to the date in the card and work on the notes and topics there.
We foment a serendipitous environment where ideas can collide with each other in two ways:
One day may contain notes and ideas from different topics.
Different days will be reviewed during the same session.
An iterative review of the Daily Notes produces better quality notes and promotes learning.
Old notes will eventually fade away with large intervals even if an idea there proves fruitful.
It's not possible to set different review dates for writing ideas in the same day.