The ground plan for Stone 56 at Stonehenge shows an irregular shape which makes the orientation of the inner face hard to judge. As the stone rises from the ground it becomes much more regular and very nearly mirrors the flat outside. It is slightly thinner on the south-eastern side than the other narrow side. At eye level (5' 6" above ground) it is approximately 35" wide vs. 29" wide which over a width of 7' makes an angle difference of 4 degrees.
Looking north-east it is noticeable how the back of the stone lines up with the Station stone in the distance. And also how the line is close to the direction of Mid-Winter Sunrise and Mid-summer Sunset. (Without a proper survey I claim no more than "close to")
Pictures taken 16 June 2012 - click to enlarge.