Pleased by the austerities of the Devarshis (the sages), Lord Shiva, desiring to be present there, entered the earth and assumed the form of the seed, which is in the form of sound (Nada).
Just as a plant emerges from the earth, Lord Shiva, breaking through the firmament (the solid earth), manifests himself clearly. He is known as Svayambhu (self-manifested), the one who has been born of himself.
तल्लिंगपूजया ज्ञानं स्वयमेव प्रवर्द्धते । सुवर्णरजतादौ वा पृथिव्यां स्थिंडिलेपि वा ३४ ।
Through the worship of that Lingam, knowledge itself is developed. Whether in gold, silver, or on the earth, or even on a stone, the Lingam can be worshiped.
The Lingam written with one's own hand, with the pure Pranava (Om) mantra, should be worshiped. One should draw the Yantra-Lingam and install it, and perform worship accordingly.