There is now a deferral one-line installer for Flotilla/Rockpool available as follows:
curl -sS get.pimoroni.com/rockpool | bash
It will copy the github repo locally and also maintain everything up to date for you. Nothing particularly difficult to achieve manually but if you are not fluent with git it will save you time (hell I believe I am and I still find it pretty darn convenient!).
Since Flotilla is bound to evolve rapidly I suggest you run the above once a week or so, to keep abreast with the progress the Wizard of Zo @gadgetoid is aiming to deliver over the festive season, while we generally enjoy life, get pHAT and open presents… not necessarily in that order!