You can chant the OM after your physical and energetic practices. Then, meditate in stillness and silence. The ideal asana for the OM mantra is the siddhasana for males and siddha yoni asana for females. Siddhasana directly stimulates the spinal cord, making the technique more potent and confined. Alternative to siddhasana is sukhasana (happy posture) and ardha padmasana (half lotus).