The mounting base gets sandwiched between the spare carrier and the tailgate, it'll install very easily, just unbolt the spare carrier, slip this in, and bolt everything back up.
Next is to weld some "Stake pockets" to the sides of the base, made from 1 1/4" square tubing.
Here's the rack base installed on the Jeep, the stake pockets welded on the base frame, and it's had a quick coat of primer. Took only about 2 minutes to install it - remove the four bolts holding the spare carrier to the tailgate, slip the rack base in between, and replace the bolts.
Also in this photo you can see the base for mounting my jerry can rack through the spare tire center hole, that base just slips over the three lugs on the spare carrier and is held in place with the spare.
I've got a Gr8Tops Exogate tailgate reinforcement/heavy duty hinge set installed, so supporting the extra weight of the cargo rack and the jerry can rack is no problem. This rack base and the jerry can rack would install just fine on a stock tailgate without an Exogate, but I don't think it would be a good idea to put much extra weight on a stock unreinforced tailgate.
So next I've got to make the vertical brackets that will go in the stake pockets and support the rack basket. They'll be held in place by bolts through the holes in the stake pockets; I decided on bolts instead of something like lynch pins to reduce movement and rattle. The range of holes on the pockets will allow a 6" vertical adjustment of the rack height, which should be enough to put the rack above 37" tires if necessary (I've got 32's on the LJ).
Once nice thing about both of these racks is when the rack bases are installed without the racks, the only thing that's visible is the small stud sticking out from the center of the spare. The cargo basket base isn't visible at all.
On to the vertical brackets to hold the rack basket next.