I refer to placing your feet ‘sitting bone’ or ‘sitz bones’ distance apart in many standing poses. What that means is that we align our feet to be essentially underneath where our sitting bones are at the base of our pelvis.
This is more narrow than hip width and wider than having your feet together. It is the usually the perfect balance between finding steadiness as well as mobility in a basic standing pose.
The anatomical name for the sitting bones is the ischial tuberosity. When you place your hands under your bum, these are the bony points that you feel.
When you sit, it is nice to gently pull the sitting bones back a bit to encourage a curve that goes in for your lower/lumbar spine. That curve is balanced by breathing into the back and creating fullness in the lower to mid back, thus creating power, support and improved mobility of the entire torso.