Shiva Purana
सर्वोपचारवद्भक्त्या भावपुष्पैस्समर्चयेत् ॥ अथवा परिकल्प्यैवं मूर्तिमन्यतमां विभोः ॥ १७ ॥
One should worship the Lord with devotion and flowers of bhava as in all other rituals. Or else he may thus imagine another idol of the almighty.
english translation
sarvopacAravadbhaktyA bhAvapuSpaissamarcayet ॥ athavA parikalpyaivaM mUrtimanyatamAM vibhoH ॥ 17 ॥
hk transliteration by Sanscript