My own Bête Noire of a subroutine, pure tapas.
Some discrepancies between the book and video. There are two main approaches to uttita padangustasana, one is to bring the knee to the chest and then straighten the leg out in front of you as I do in the video. The other approach and the one, the one I use now is the same as in Ramaswamis book, raise the leg straight up in front of you and then take hold of the big toe.
I noticed Ramaswami has us raise the leg on the exhalation, I've always done it on the inhalation, I tried it his way this morning and I think I like it, it feels more controlled, focused.
In every stage we should aim to stay for three long, smooth breathes.
Ground your standing foot, from the big toe to the heel.
Ramaswami recommends engaging the bandhas, see guidelines Day One, basically, draw up the anus and suck in and raise the belly at the end of the exhalations and hold.
Uddiyana bandha seems particularly effective for keeping the leg raised, really suck the belly in and up into the ribcage as much as possible while holding the leg out straight.
Sucking the belly in will also give you more room for folding over your leg.
When folding forward to bring your forehead to the knee, push the hip/buttock back, remember your uttanasana.
Lift up the buttock of the raised leg, I visualise that it's supported on some kind of Subway standing lean/seat
Don't drop the pelvis when swinging the leg around to the side
The squat is on the long slow exhalation, strong ujjayi will give more control
I find the squat here the easiest of the one legged squats, the outstretched leg with the foot held seems to give you more control as you lower.
Folding over your leg in the squat imagine a rope attached to you foot and another to your hips and that your being stretched outward, your still wanting to be pushing your backside out in this forward bend.
To come up engage the bandhas strongly, press through the mat, raise up slowly with the inhalation.
Coming up from these one legged squats is where you'll start to think there may be something to bandha work after all.
This is an intense hamstring stretch and forward bend so make sure you are nicely warmed up. The utkatasana and uttanasana half and full subroutines from the On your feet sequence would be one way to go or perhaps the Utthita parsvottanasana. The latter is an intense hamstring stretch itself but it's possible to work into the stretch in that subroutine.
Work up to the squat, lowering a little way and then coming back up perhaps on the breath. if your wobbling and swaying too much don't try to lower all the way or you risk spraining an ankle