I introduced the rough/smooth board to E(1) last week.
To make the board (I made it about 3 years ago for O), I glued a square of sandpaper on one side piece of foam core board and left the other side empty.
To introduce the board to her, I lightly rubbed E's finger on the sandpaper and said "rough," and then I rubbed her finger on the foam core board and said "smooth." She repeated the words after me, and seemed to understand completely. Simple, yet effective. She also really liked scratching the sandpaper with her fingernail :)