Is it possible to have my e-commerce on a subdomain in Shopify?

Site URL: https://www.chrisspecialtyfoods.com/

My client wants to migrate ecommerce functionality to Shopify. 

The idea is that the "Shop" button redirects to shop.[site].com, instead of [site].com/shop. 

Shop.[site].com would be on Shopify, and the rest would on Squarespace.

I'm not great with DNS stuff and have been stumped on this project for many hours now.