Here’s the article on the way you should work when setting out a geometric Roman border pattern. It seems quite involved at first but it is all about developing a way of working which allows you to eventually work with the bare minimum of markings. A bit like learning to drive a car, it’s really confusing at first trying to remember everything you have to do and it what order but after a while you can do it all without thinking.
What order do I work in? Geometric Roman mosaics