Put in board 50. Reverse. Add row, board 2A. Crop board 50, I-Y. Crop. Done.
What is confusing is that it looks like the boards go in two different directions. If they did there would be no way to align the real boards because the columns would go up-and-down on one board and side-to-side on the other. They do not. Board 2A is aligned with its columns up-and-down just like board 50, and as long as board 50 is cropped right, the layout just works.
JR