Marine flatfish (4)
(Other definitions for sole that I've seen before include "A fish; part of shoe" , "piece of leather" , "Underside of footwear" , "Just one - fish" , "Bottom of the foot" .)
(Other definitions for flounder that I've seen before include "Be out of one's depth" , "Fish; stagger clumsily" , "thrash around wildly" , "Move clumsily like flatfish?" , "Have difficulties with the flatfish" .)