So it seems that what people are eternally learning is that you do not need large blocs of time in which to do work, you just need to actually use the time you have. The claim of needing large blocs of time is a delaying technique.
I agree, but with one caveat: they do not want to give us large blocs of time during the week or during business hours, so of course the sensible advice becomes to use small blocs of time. This is convenient for them.
Still, I am not one of those who requires large blocs of time. My actual disagreement, or alternative focus on the question of time is twofold.
One, as I have said before, you must allow yourself to estimate time realistically. Perhaps it really will take 120 hours total to write that piece. If so, it is of no use to try to force yourself to take less time; you have to plan to free up all of the 120 hours. On the other hand, you may only have a certain number of hours in which to prepare a class, grade papers, write a report. That is where you must drop “perfectionism” and fit the task into the amount of time you have.
Two, as I have also said before, you have to be relaxed during your time — the work and your power, not your superego or anyone else’s, have to be the only entities in the room.
But a famous writer has just been here and said he needs large blocs of time. On a writing day he dreams himself into the characters during the morning. He writes all afternoon, and sometimes in the evening. A day on which he speaks, or teaches, cannot be a writing day, he said.
So, smoke that. Does he believe it merely because he is in a position to live in this luxurious way, or is it actually true of those who really put writing first?
Axé.
coldhearted scientist وداد 
Or does he say it because he thinks that is what people want to hear, or because it is self-serving; that is, he might not do that, but he might be invested in keeping other people from having the life of a famous writer, so he makes it sound like there is no way to move from ordinary life to famous-writer life, since we mostly do not have the luxury of spending whole days on dreaming and then writing.
Cynical, moi?
Do the thing that works for you.
I’m for either/both. But I tend to get very involved once I start anything. And if I’m really started, any amount of time, small or large, can be put to good use.
I think all the regular advice is frustrating if you already know/use it, and then try to use it as a solution to other problems (e.g. doubts about how the project is framed, that may be legitimate and deserve attention as opposed to exhortations about the need to avoid perfectionism).
Also, in the period when I was blocked on academic work, where it first showed was in writing but the real issue was that I was blocked on everything and needed to address that (not “time management”).
If I thought about the 120 hours at the beginning of a project, I’d give up, right then. Only by lying to myself about how long it will take can I ever get started.
I’ve always been pushed to go faster and faster. If I don’t give myself enough time, all I can think about is how I must race. I am not slow to begin with.
Those people who set timers really amaze me.