Sinking is ‘dynamic’. Gravity is a continuous stream, never-ending downward force that flows into and thru everything on the earth. It falls into you and you fall into the earth. Proper alignment of the body, openness of the internal spaces and alignment of the mind are required to be skillful in sinking.
Initial practice is done in the standing postures. Relaxation, the ability to ‘let go’ is developed by standing. Once you begin to feel the continuous ‘downward flow’ then the next step is maintaining the ‘sinking connection’ while moving slowly (tai chi).
Alignment of the mind refers to ‘ting jing’, the ability of the mind to be quiet and using its ability to ‘listen’ and ‘feel’ the downward flow.
Then it’s a matter of practice, practice, practice.