I followed the pattern with the following exceptions:

I slipped the first stitch along the edge of each triangle or rectangle where the stitches for the next tier would be picked up, which makes it easier to pick up those stitches evenly.

I didn’t like the weird jog that is created along the cast-off edge at the start of each new triangle in the final tier, so I replaced passing the last stitch of the previous triangle over the first picked up stitch of the new triangle with the following:

1) Pick up 10 purlwise, turn
2) K8, sssk, turn
3) p8, p3tog, turn (continue as per pattern)