Writing direction on seals
The general principle is from top to bottom, from right to left, but the format can be very flexible. For a four-character seal, there are 6 ways to arrange the characters (see picture). Seal calligraphers normally pick the arrangement that is most aesthetically pleasing, depending on how the character is written &amp; number of strokes per character, etc. The only exception I'm aware of is for 4-character seal, the 2nd format in the picture breaks the right-left rule but that particular one has a particular name called 回文布排 ie "anti-clockwise" that is for 4-character seal only. 

picture taken from http://www.shufazidian.com/shuji/article.php?acid=21&amp;arid=41