I have an informal method
I have to write complex reports for work. They contain some data, observations, conclusions, recommendations. They are about 4 to 5 pages long.
When a report is in the "getting generated" stage, that is when I know I will be getting the data, then I start writing and after I get the data I write at least one part a day until it is done. Sometimes, it is just the heading and reason for the study. Sometimes, I have eyeballed tha data and the results are so robust that I can write a tenative conclusion and recommendation before I have written up the data. The later is tedious and requires total alertness so I do that in a high energy mode. My n/a is just "write part of report" unless I am stuck and need to do something very specific like locate a reference or check the data and make sure that the columns add up.
I could save myself a lot of time if I had templates and outlines but I am so poor at using the features of the computer that I don't. Also, sometimes one part of the report requires more careful thinking and wording than another and I often want to do that first.
I have read that the most productive writers, write about the same amount every "work" day. I think that one of the bigger challenges is keeping ones notes, references, etc. organized and accessible. I have also found that when I am blocked and can't write, it helps to write about why I am blocked.l