I could do up some plans if you want. I just kind of winged it. I started with a cardboard cutout of the bottom.
I found the second row seat could be used with a 40" length and a 12" total height.
I scribed the cardboard around the wheel well and then cut it so the PS 3rd row seat could be used.
I then put on the two sides. One toward the third row seat and the other just inside the wheel well.
That gave me how big the back piece of the box was.
I then used another piece of cardboard to make the entire top.
Cut that piece.
I then marked the DS edge of the drawer box and cut off the side hatch.
I then cut the top into 3 pieces for the hatches on the drawer.
Then I cut piano hinges to the needed lengths and put the top together.
I did notch out the side piece to accept the piano hinge so the piece was pretty flush to the rest of the top.
I put a 1"x 2" for the side piece to rest on, however I may need to add a gusset or two. Then installed the top.
Now I had my box.
I then measued how big I would need the floor of the drawer, cut it and made sure it fit ok.
Then cut the back, sides and front of the drawer, put together, and pre fit them.
Then added a full width front piece.
Voila.
I used 3/4" G1S fir plywood for all parts.
I countersunk and pre drilled all screw holes and used #8x2" screws, except I used #6x1 1/4" screws on the 1x2 and the drawer front, and #6x3/4" screws on the piano hinges. TY you are from Canada so be sure to use Robertson heads.

I glued all of the pieces together with PL400 adhesive.
I also presanded most of the pieces with 80-120 grit on the belt sander and gave it a good sanding after and rounded off the sharp edges.
It was pretty quick and dirty. My table saw was locked in my neighbours garage who is out of town, so clamping a straight edge and using the circular saw added a lot of time. A belt sander is good to hide some of the imperfections.
Now I need to get hardware. Pretty tough in this small town.
Hope that is not too incomprehensible.
Pretty much just a box inside a box with an appendage on the DS for the side hatch.
Sean