Today I started to arrange my HTML elements on my web page to match my mockup.
Then I styled the border for all of my classes with a red, 1px, solid line border. I saw this trick on Twitter where you can better see the elements on the page as you're styling. It helped me a lot to visually verify what I was doing in CSS.
I mainly used flexbox again since I don't know any other way to move the elements around without statically inputting values. I'm a little unsure if this is how I want to keep it, but I will stick with it for now.