What is the best way to create your own template through HTML?

Vittoria, we do not have a handbook that would provide guidelines for creating responsive content using HTML. You can use our Drag and Drop editor and insert a Code block where needed to have your own code. Please note that we do not troubleshoot custom HTML or instruct how it should be written. The Code block and the HTML editor are simply additions for developers who wish to insert their own content. Also, we always recommend to explore all options our editor suggests - it is powerful and has loads of features. More often than not it’s possible to achieve your goal by simply using the editor. Thank you!