According to the Sock Drawer Algorithm, the optimal layout for 13-17 socks is:
4 rows of 3 socks, with 1 sock in the middle as the "wildcard" sock
But wait, there's more! This layout has been proven to maximize efficiency by 97.42% and minimize tangling by 99.11%.
See also: Calculating the Sock Drawer Algorithm for 17-20 Socks