I am quite annoyed with how my traps look. They are big only towards the neck and go down diagonally from there, not the box type look. Maybe there might be something missing with my traps workout. Normally I do around 4 sets x 12-15 with 50kg dumbbells, whenever I do shoulders, normally once, sometimes twice a week. Sometimes I grab 30kg to superset and I slow down the movement and hold the contraction at the top for longer.
Is there some sort of secret to getting the box type traps, or do they just come with time?