Another method to remove the floorboard AND be able to put a one-piece floorboard back in place is not mentioned in that excellent Tech Tip.
After removing all the bolts from the side-perimeter metal flanges, one of the metal flanges has to be removed. This not only allows the whole floorboard to be removed, but, more importantly, it allows a one-piece floorboard to be installed.
The side-perimeter metal flanges are each attached by more than 20 spot-welds (as I recall - I counted them once). Those spot-welds have to be drilled-out from one of the flanges, and then that metal flange can be removed.
Then, the floorboard can be angled-upward and be removed from the top (or, maybe from the bottom, but that would be interesting to accomplish). I do not know if the rear cross-sill has to be removed in order to get the sheet in or out of the rear door opening.
I have only seen one person report using this technique (no photos were provided). I have not seen any other technique that allows a single-piece floorboard to be removed/installed.
A wide piece of plywood is needed, if you want to replace the floor as a single piece. Supposedly, some boat repair facilities will have available a piece of appropriate thickness plywood in a large enough width (at least 54" wide, as I dimly recall).