When using Spring + Spring Boot + STS, where in the Spring Project directory is the localhost "home" folder?

I am using Spring/Spring Boot/and Ember. I want to put my index.html file in the "localhost" main folder, but I have no idea how the Spring Tool Suite deploys Spring Boot. What is the normal process for HTML development and accessing a Spring REST server without getting Cross Site Scripting errors?

My folder structure is as follows:

/.settings
/BookingClient
/gradle
/html  (this is where my index.html, css, and all Ember related JS stuff is)
/node_modules
/src
/target

I am guessing its somewhere in the /target directory but nothing I have tried has worked.