This is a very new stitch. I have never come across this stitch before, may be because this stitch belongs to counted thread category. The stitch is explained here on Queenie’s blog along with links.
This stitch involved four steps for its completion. The first sample is the stitch in different stages of progress. The polyester was not ideal for working this stitch. The second sample worked in cotton skein is the basic stitch.
SSS.74. boust-1
The stitches are worked with spaces in the 1st row. The tall and wide version of the stitch are alternated in the second row.
SSS.74.boust-2
The stitches are worked to create borders in this part of the sampler.
SSS.74.boust-3
In the first row, after working the half crosses, only the second and fourth steps of the stitch are worked alternatively, resulting in this sample.

In the second row, the half crosses are worked like this\ and /  alternatively and pulling stitches are worked on them. If this sample had been worked with spaces between stitches, it would have given a better view of the detail.
SSS.74.boust-4
The first and the third steps [half crosses] are worked with space in between them [not worked through the same holes] and the stitches were worked on them in the first row. The stitches are worked in two colours in 2nd row. Upright versions of this stitch were tried in the last part of the sampler.
SSS.74.boust-5
A stitch which adds texture, have to look into the ways of using it.

The whole sampler

SSS.74. Boucle stitch sampler