C&C Question about coroplast!

Hi all! After doing research for nearly a month now on guinea pig care, I am finally getting one of my own! I have had rabbits and hamsters in the past and currently so I know what work they require and that space is needed.

I am planning on building a C&C cage. I am going to make it 2 x 4 cubes. The cubes are 14". I was just wondering how much coroplast to buy for the bottom. Also, how much fleece would I need? Thanks so much!