From what I can gather, the idea is to go into your stash of yarns, pick out a colour palette you are happy to work with and the kicker - once you join the new yarn in, don't stop until it runs out! Yes this might mean you have four rounds of green and only one of dark blue but it works out awesome in the end! Before you get started, here is a tutorial for the lovely Double Treble Stitch.
To create the centre:
Row 1: Ch 20. DT (double treble) in 3rd ch from hook. DT to end. Turn.
Row 2: Ch 3, DT to end. Turn.
Repeat Row 2 - 7 times or until centre bit creates a square shape. Bind off.
With same or new colour join in any chain space.
Row 3: Ch 4, DT, in ch space. (Ch1, DT, Ch1, DT) repeat until next corner.
Corners consist of 3 DTs separated by 1 ch. Each new cluster is placed in between the second and third DT of the row below.
Continue with the (Ch1, DT, Ch1, DT) pattern in each ch space creating a giant spiral. Join new colours as needed.
Bind off, darn in ends.