Depends in the effect you want to see.
Most plank effect areas start with a full piece, or nearly if it leaves horrid cut at end of the run.
The second run starts with the off cut from the first. It becomes a totally random bond giving the most life like timber finish.
If there’s a timber floor you can view you’ll get the concept.
Symmetry doesn’t work well.
You can still mark out from centre, but for example, take the far left corner and measure up where your cut will end and take the offcut and place it in position of the next course and work out the next top cut, then put that off cut centre or your shower. 😁
Employ same technique to your wall as in the end of this floor in the window area
You’ll have to enlarge image probably.