Hi Sonia , you could try some things with a foam roller, but it may be too large and too unsteady. Do you have the foam roller that is cut in half? That would be a better one to use. Or if you have a small Pilates barrel or even a large towel rolled up. It just needs to be a slightly raised surface to assist with extension but not too large.
Watched for the second time, absolutely loved this work as I have runners and cyclists who find squatting and lunge work very difficult. Loved the idea of bolster/ towel