A small left-right movement from the centre of the belly. Presence does not need stillness.
Sit with your back straight.
Feel gravity: let your weight drop into your feet or the seat. Feel your weight being held by the seat or the ground.
Find your axis: the line from the pelvis to the crown of the head.
Begin a very small, rhythmic movement from side to side.
The movement starts from the centre of the belly, just below the navel.
Feel the rhythm like a pendulum; the axis always returns to the centre.