Blank Slate is a "Platform as a Service" solution. PaaS solutions typically offer an integrated IDE, either on the desktop or in the browser, which you use to build your applications. Blank Slate happily offers no IDE. Instead, Blank Slate offers APIs. The Blank Slate APIs allow you to create the server side things you need -- including things to manage your data, users, and applications -- without touching a line of server side code. You just tell Blank Slate what to do thru the APIs. Blank Slate is very obedient.
Because there is no Blank Slate IDE, to use Blank Slate you need to know how to make web pages and connect to APIs. Why did we make Blank Slate this way? To give you the freedom to make the things you want and need, and to work with the languages and IDEs (Visual Studio, Dreamweaver, Eclipse, PDT, even Notepad) that you already know.