The pitcher comes set and checks the runners.  As the pitcher goes into their motion, the 1B comes off the bag to get into their field position.  As the runner, take your lead off the back off the base to help stay out of the vision of the 1B.  The runner DOES NOT take off on the pitch.  The runner instead takes their secondary lead (two hard shuffles)  - but instead of stopping, the runner takes the two shuffles and takes off for second just as the pitch is crossing the plate.  Typically, the 1B will have their back to the runner and not see them take off because it is delayed.  The SS and 2B should be late to cover the bag.