The best thing you can ever do when you are looking at strand or to give them their proper name, guilloche, patterns is to imagine them as three dimensional objects. They need to be something that you can imagine grabbing and hold of and pulling apart. The strands go under and over each other, don't have the strand stopping when another goes over the top of it, 'see' it going underneath the other.
This helps you to understand the structure, the way the pattern is created and it also helps you when you set the last tesserae. They need to set facing the right direction, this is why, when you do a short sectio of border pattern I suggest you have the pattern drawn on paper and this is then put under your baseboard so you can see how those tesserae at the edge need to be set.