I wrote four such books. My first one was 750 pages. The others ranged from 250-400 pages each.
My technique was to budget a particular number of pages or a particular amount of time each day to write.
For myself, I found that if I wrote more than about 4 pages per day (6 on a good day, it varied), I would quickly get burned out.
That's 2000-3000 words.
For the general structure, I wrote an outline. It doesn't have to be very detailed, just enough to guide you along.
Don't write your introduction until you are finished. I always wrote that stuff last.
Don't bother with perfection. Your publisher has copy editors, technical editors, and so on for a reason. Let them do their jobs. On the flip side, remember that they are not programmers, and when you use words like "OR" as a verb, you will confuse them.
Find a part that interests you, and write it to get with your own flow.
There are less interesting parts to write. Power through them. 487
Do not allow yourself to get to a more interesting part without first going through a less interesting part.
Sometimes, even when trying to budget per day pages or words, there will come some days when you just can't write 2000 words. You try your best, but can only squeak out 1000. That's OK. However, do not make the next day have to be a 3000 word day to make up for the lack, or you will reach a point when you need 10,000 words, which is nearly impossible to make good content for, and it'll overwhelm.
If you have a light day, spread out the shortage over 5-10 days. If you short by 1000 words, add 100 words per day until you make it up.
Take days off. Seriously.
Also, if you get through your budgeted words or pages, and feel like you can double it, force yourself to stop and not write anything until the next day. Trust me on this. You can write a little bit extra, about 25% or so, but don't double. Burn out city. 487