I write (only for fun) and generally I start with an idea, write my way into the characters (getting to know them and the setting), and then set them on their journey.
It's much like a real journey in that I usually know a few stopping off points along the way, and have a vague notion of whereabouts the ending it will be, but I don't know the exact route or what it will all look like, what will happen along the way.
Sometimes I get lost or hit a dead end and have to turn back to an earlier point and restart. Sometimes I go on a diversion and it's unexpected and completely wonderful.
Sometimes it peters out completely and that's my loss - it goes in the bottom drawer.
At the end I go back and redraft and often lose the first few "getting to know you" pages.
I always write chronologically (though I sometimes rearrange slightly afterwards) but for me it would be too weird to do it any other way, as the character development would be all out of wack if I wrote later pieces first.
However as others have said, I think there are as many ways to write as there are writers! Someone (might have been Stephenie Meyer?) apparently writes all the fun scenes first and then goes back and fills in the gaps. In an interview they likened this to eating the nice bits of your meal first then eating the vegetables!
Someone else (might have been Hilary Mantel about Wolf Hall?) said that she wrote just vignettes in no order, then later stitched some of them together into the novel, some didn't go in at all.
Arthur Ransom's method sounds terrifying! For me a really detailed synopsis would kill the fun - if I know what happens, why travel the journey? There needs to be some suspense for me otherwise I won't care enough to keep going. But that's just me.
Good luck - I would recommend just pitching in and seeing what happens, and if it doesn't come together that doesn't necessarily mean it's your fault, sometimes an idea just won't sustain 100k and it can be hard to tell that at the outset.