I stretch both legs, first one then the other; I just wait until I can grab my toes and then ease a stretch on the hamstring until I feel I can breathe. I suspect it’s years of half-lotus on both sides that now enables me to get into the lotus, but there are specific coordinations that I call to mind to stay in the lotus and relax. The hamstrings and the quads reciprocate activity out of stretch, and that puts a stretch on the ilio-tibial tract. Stretch in the tract generates activity in the sartorius muscles that pivots the pelvis on the hips, left and right; with that pivot and stretch in the ilio-tibial tract, activity will be generated in the gluts that also pivots the pelvis left and right on the hips. Not volitive activity, activity generated by the stretch of ligaments and fascia that translates into different motions.
The left and right pivot of the pelvis on the hips puts the balance forward in the lower abdomen, and that slight stretch generates activity in the obturators that extends the hips slightly from the pelvis. This allows the activity of the legs from the soles of the feet to travel up the back of the spine to either side of the skull and the top of the head in inhalation; the return from the top of the head to the soles of the feet depends on the free movement of the mind , technically the free occurrence of consciousness, and the stretch and activity occasioned as consciousness takes place for the complete exhalation. That’s because it’s really about the generation of the cranial-sacral rhythm by nerves at the sagittal suture, so the real return is in the motions of the sacrum and the way the rhythm extends through the body.
In short, it’s the sense of place, the one that moves in falling asleep (and in waking up, although that’s harder to see). That’s the source of the action. The more you see it, the more you can rest in it, and so you gain it.
That’s how I sit in the lotus. Why it took so long to be where I am, I can’t say!