Answered by Shaykh Faraz Rabbani
How should I sit during the Khutba?
The essence of the sunnas of the one listening to the khutba is that they should be silent, attentive, and reverential.
As such, it is recommended to sit as one would during the prayer, for those reasonably able to do so. This is a general recommendation, however: one can also sit cross – legged or in other comfortable postures, without it being disliked because the khutba is not actually part of the prayer (in which the posture is a confirmed sunna for those able). [As mentioned in al-Fatawa al-Hindiyya, quoting al-Mudmarat and Mi`raj al-Diraya]
And Allah alone gives success.