Customizing the Filter Box (way it appears on the collections page)

[Nicki3]

Hello! I am looking for a way to make the filter box on the collections page more visible so that customers know to use it. We have around 1000 one of a kind rugs that customers would search by size (length and width). Using collections isn't working well because the grouping is rather subjective- one person's large is another person's medium, etc. I want to have all of the products in one collection and make it very clear that you need to input your desired width and length. However, the filter box is so tiny that most people just scroll right past it. Then they keep scrolling and scrolling and exit. Is there any way to make this larger and "louder?"