I knew from the start that I wanted a banner on the top and 3 columns under it, with the middle one being the widest and having the content, menus on the left and various stuff that I want visible on every page on the right. I wasn't skilled enough to build a template from scratch, so I started with a premade one that I modified. It introduced me to
flex containers, and they're my favorite thing in CSS. The footer wasn't planned from the start, but I got so excited about rediscovering small graphics that I wanted them visible. But as they're not the main thing, I put them at the bottom of the pages for anyone who wants to look through them after finishing the content. My top bar with the light/dark switch and the jump to content and a greeting for signed in people was also added later. Jump to content needs to be at the start or it defeats the whole purpose, which in my case was to give people who navigate with tab a shortcut so they don't have to click through the whole menu before getting to the content.