lifts up place height under the sitting bone of the straight leg.
The next three pictures are even more variations if you find it difficult to reach the shin or bolster across the shin.
In all the variations, with or without support under the hip make sure that the legs remain active. Keep the outer thigh of the straight leg rolling in, kneecap up, press out through heel. Press into bent leg shin. That action will help keep the spine lengthening up from the base of the spine.