Buy four pairs of Finnish military M05 liner socks. You need them anyway and get the 4-pack cheaper! The new basic sock of the Finnish Defence Force. These socks work well with any lined boot and together with a thicker pair of socks they make any non-lined leather boot much more comfortable.

Only want one pair? Here they are.

Like any sock from the Finnish armed forces, these will keep their shape and fit well throughout years of use. Being made of a merino wool blend, they combine the warming and moisture-wicking properties of the wool with the durability of synthetic fibers. Originally intended as a liner sock, they perform great as an all-around sock for every day use.