After exploring the question posed in this thread, I am puzzled as to why setting the slider's scroll direction to vertical does not result in smooth up and down scrolling. Could this issue be related to slick itself, or perhaps the accompanying CSS code? Check out http://codepen.io/anon/pen/VeELqN
Even without the CSS code, it seems that vertical scrolling is malfunctioning and incorrectly calculating the top y position for the next slide.
I'm unsure what specific code details are needed to overcome this obstacle, but here is how the slick object is initialized:
$('#slider').slick({
autoPlay:true,
dots: true,
arrows: true,
vertical: true,
});