Hi Ben
Yes basically you need to make sure your boot floor side panels are good, if not you need to repair them so that you've got a good lip to sit the checquer plate on.
Also the same applies for the rear and front edges, either repair your panels or weld a strip on to sit your new boot floor onto.
You will be the boot floor braces underneath, I cable tied fuse to the chassis mounts to locate them.
Once you have your floor cut and test fitted, remove it and apply sealant around the outer flange where the floor will sit, and then drill and rivet all around.