The board to the right of the leftmost board has to be an irregular shape due to the uneven space of the area.
Lisa took one of the 2x6 boards and rough-cut the wedge here, then started trimming the board to fit.
Using this wood rasp (she wore her respirator while doing this due to the nature of the sawdust coming off of pressure-treated boards), Lisa did a lot of "cut-and-try" work until she finally got the board so it fit into the available space.
It may be more obvious at this end, with the "keystone" board being the next-to-the-rightmost board, that it's both narrower and irregular. However, 15 mm isn't that much and it may not be that obviously unless you know what you're looking for.
So here are all of the boards in their final shape and fit. Only the one closest to the camera has been fastened to the supporting beams. The boards have all warped somewhat, but Lisa expects that with enough wood screws, she will get the boards into the beams, and that they should adjust to the new shapes soon enough.
I say this is only the end of the beginning approaching, because there will be more work to do once the deck is in place, but we are still happy with the progress Lisa is making.