Writing top-down bottom-up and round and round

I had a crucial meeting with my PhD supervisor today. I basically declared that I have fiddled about long enough and I am now writing my thesis. I have about 300 days to go and University policy dictates a thesis 80,000 words or so.

I will have to approach this from many directions, a bottom-up approach will be to write 300 words per day consistently, this will form the oodles of clay that needs to be pushed around to give the thesis body. Top-down approach my supervisor recommended was to structure my thesis with chapters and sub-headings and write 2-lines about each sub-heading, this will come to about 2-pages and form the armature of the thesis.

People do their PhD's on a single track and their theses are like great big towers. Some collaborate widely like Erdos and end up PhD's which look like the Savannah ( I was going to say sahara but that is not true, there are splashes of greenery). Mine is ending up like a Nautilus, starting from a point, fidgeting about and organically growing in spirals.