Starting width and ending width are the only things you need. All the different end seam locations are random. I'm just saying that you don't need to do any plank layout between the beginning plank and the last one.
Once the first row is in, you set a couple of planks in the second row and be sure that you don't end up with a two inch piece at either end.
Same with the next row. The whole process is about putting down planks and offsetting the joints in each successive row.
Once the first row is in place, lay some planks in the next two or three rows, staggering the joints so it looks nice. With those planks loosely placed, measure an approximate cut length of your first piece, then see if the remaining piece will fit at the end of the next row or the row after. Get a straight row installed, then just start installing.