Note that on my build there is no "trash can hole" in the door to the undersink, which I like because it's a cabinet for me.
The sink trap hangs down in the main part and there is a shelf to the left about 1/2 way up. Also my grey water tank is partially in the space and the grey water drain comes at a 40Âº angle toward the door- across the whole floor. Add the sink lines in the back and across the floor, and it is really a mess in there.
The space is my junk drawer because it is so misshapen. Nothing really big can fit (a kleenex box is about as big as any one thing that can be maneuvered on to the shelf easily), I have a spare water line, my water fixtures for inside filling, box of walmart bags, extra paper towels, a gallon jug of water (can only go in front of the door), and probably a bunch of things I've forgotten.