What is the proper way of sitting while eating according to the Sunnah? And what is the evidence for that? Does the licking of food apply to drink? And should all supplications be recited after eating, or should they be varied?

It is from the Sunnah (definition) to sit for eating by kneeling on the knees, or by setting up the right leg and sitting on the left, following the example of the Messenger of Allah, peace and blessings be upon him, and out of humility to Allah. This posture is also the most beneficial for the body.

Moreover, no food or drink residue should be left in vessels, and there is no difference between them in this ruling, due to the generality of texts that command the preservation of food and drink, and because the blessing may be in the last remaining portion of it. There is no validity to narrations that contradict this meaning.

It is permissible to leave leftovers or remnants if they contain harm or damage, or so that others may benefit from them. However, merely leaving them without reason is not prescribed. The authenticated supplications after eating are commendable, and one may recite whatever is easy to do so.