Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) says that when the Messenger of Allah (peace and blessings be upon him) ascended the minbar - or he said: sat on the minbar - we would sit facing him (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5711