There are 8 twill squares. Green is the warp and one of the other three colours is the weft. Here's my favourite in the warm siena brown in a 3/2 twill.
I did two different tartan patterns.
One based on the proportions of a Graham tartan.
One based on the proportions of a Campbell tartan.
All the ends were left at the edges and caught lightly onto the back afterwards.