The expression “laying the foundations” is a metaphor often used in the alchemical texts. To build a house, one must first lay the foundations. Only when the foundations are stable and firm is it possible to set pillars and beams in place, and arrange bricks and tiles. Refining the Internal Elixir is based on the same principle.

The alchemical practice, however, is concerned with the human body. At the initial stage of the Neidan process, therefore, one should first replenish the basic constituents of the body, so that they conform to the requirements of the practice. Only then is it possible to undertake the stages of alchemical refinement proper. Until the basic constituents do not conform to those requirements, the body's functions should be restored and augmented by means of inner practices, so that Essence, Breath, and Spirit can reach a state of abundance. All this pertains to the stage of "laying the foundations."

Human beings receive this Golden Elixir from Heaven. It is perfectly good with nothing bad in it, it is innate knowledge (liangzhi) and innate capacity (liangneng). It is the Numinous Root, entirely achieved and with nothing lacking. It is the Breath of precelestial Perfect Yang. . . .

Golden Elixir is another name for one's inchoate fundamental nature (xing). There is no other Golden Elixir outside one's fundamental nature. Every human being has this Golden Elixir complete in oneself: it is entirely achieved in everyone. It is neither more in a sage, nor less in an ordinary person. It is the seed of the Immortals and the Buddhas, the root of the worthies and the sages.
 

From Liu Yiming's (1734-1821) commentary to Poem 3 of the Wuzhen pian (Awakening to Reality)