Make A Single Page Outside My Cart Directory?

Is there an easy way to make my index page look/work like all the pages within my cart even though they are in a sub-directory? Many years ago I had an old cart in my main directory on my site so when I moved to CS I had to move it into a /shop/ sub-directory to avoid overwriting old pages. Now my index page is outside of that directory I just have a generic landing page that is optimized for SEO but looks horrible since it doesn't really match my site.

I know I can design the page to look like my cart pages but that will be quite time consuming. I could also just forward my index page to my /shop/index page but that probably isn't the best for SEO so I'm just wondering if there is any way to do what I need to do very quickly?