The position in which man was created by God is the standing position. This is our natural position, the position in which our person is fulfilled and behaves as it should. That’s why we see the saints in most icons standing.
Hence the best position for prayer is the standing position. The kneeling position is tiresome and it is used only for short periods of time during intense prayers, fact which is specified by the typikon. Sitting on a pew is a relaxing position which weakens our concentration and that’s why this position should be used sparingly, only when someone is tired, old, weak, ill and so on.
Some ascetics have other positions but these are outside of mainstream.
In this photo is depicted the Gospel prayer from the service of the Holy Unction