I'm still searching for it. Squarespace can't be the best option.
For someone like me, a CSS and HTML novice, Squarespace is easier to customize than Wordpress. You have to customize because an elegant, simple, blogging template doesn’t exist, in my opinion. As long as you are writing text-only posts, Squarespace’s iOS app is decent. You can easily write your post in Ulysses and paste the Markdown straight into the Squarespace's Blog app. And you can easily edit a post in the Blog app without having to open a browser.
It stinks, however, that Squarespace is basically inaccessible from a mobile browser, which means you cannot tweak the design of your site away from your computer. Even on a computer, customizing the site or editing a post is driven by a sidebar menu that buries settings in submenu upon submenu. Editing a draft or finding the button needed to write a new post is far from elegant. I should do a screen cast to show you all the little pop-ups and invisible menus that appear as you hover your mouse across the screen to find the Manage Posts button. Oh, and if you want to include pictures in a post, don’t even think about it until you get to your desktop or laptop. But when you finally get to your laptop and open your Markdown post in a browser, good luck with typing your first edit in the correct place. Your cursor will likely be in one place, but when you start typing the words will appear either one line down or one line up. Hopefully, you are just working with a Markdown box and not HTML. If you are working in an HTML box, then apparently you have to insert custom CSS to get your hyperlinks to show up in the right color. Finally, it seems to me almost every Squarespace template is designed to be an online store front or art portfolio. This template is the closest thing I could find to a clean, minimal, template for text-mostly blogging.
Whether using Squarespace in a browser or mobile app, the platform feels clunky and disorganized. There has to be something better out there. I wish the Ulysses folks would create one.