Relatively simple square, 90 stitches across by 82 rows.

Gauge not really important, size can be changed by changing hook or yarn. Three different colours needed, suggest grey, white and black to match the colour system described in the book.

If you don’t have three yarns all the same weight, I’ve found it works fine for one or more of them to be two strands of a lighter-weight yarn crocheted together (I personally had to use two strands of DK for the grey).