I never understood how flexbox worked and I tried grids but they turned out to be more trouble then they were worth. I am old school and use float or text-align to align things left or right. Margin:auto or text-align:center centers stuff just fine too. I used to use the old align html tags, but those are now deprecated apparently so I try to avoid them now in order to keep things up to date.
I am also a big advocate for tables. Tables are extremely versatile and easy to use once you understand them. Sure we have all kinds of fancy css now a days which is better for layouts, but I have always used tables and they still work great.