What's left after the seat is out is not flat with the back end. I also put some black duct tape over some wires to keep them from getting caught on anything.
I had a 2x3 foot piece of thin plywood left from another project, so I laid that over everything and had the front edge even with the raised part of the floor. That leaves enough space I can set Rubbermaid totes on the floor behind the front seats. You could alternatively use much thicker plywood and have it reach clear to the backs of the seats, that way it could hold more weight where there is no support underneath. Be aware that your plywood "floor" will angle upwards a bit because of the raised metal bits underneath.
I simply turned the cargo mat around to cover the plywood to make things look better. I don't have the plywood bolted in place yet but will probably do that next.
I didn't take any pictures while removing the back seat, but there are some big bolts you need to take out on the bottom and also the sides, and some of the seat belts will come out as well. I never have anyone in the back anyway so that doesn't really matter in my case. Be aware that the seat backs are VERY HEAVY and may require two people to get them out of the car.
Besides hauling a lot of stuff, or big items, you might try this for camping and put an inflatable bed in the back, and after you're parked you can even move the front seats further forward to give you more room. I have three king-sized fleece blankets I put down, over and around whatever I'm hauling so that the interior stays in good shape and doesn't get scratched up.