Matt,
It's basically a 3-4" deep, 1/4" plate steel pan (bottom and all four sides) that is welded in between the firebox and the cooking chamber. And the water fill is a hole that is on the left side of the pan, at the bottom edge, so when the water drops below 1\2 full in the pan, then a bit of smoke exits at the top of the water fill to let you know it's empty.
There is about a 1/4" gap between this welded in water pan, and the sides of the actual cooker, which is where the smoke comes up into the cooking chamber. Very simple design, works great, with or without water in it.
The deflector plate sits directly below the water pan, with an air gap between the water pan and the deflector. This is so the water pan is heated indirectly and the deflector plate takes any heat abuse. Deflector plate is just a rectangular piece of 1/8" plate that can be replaced if needed (it never will...the fire is so controlled in the LSG that there are never any flames, etc)
I can take a pic for you later today, but it is deceptively simple and pretty uneventful!
That's the best part of the LSG IMHO, simple and overbuilt.
Not a fancy/showy pit, no special tricks, etc, just a beast of a smoker built to last a lifetime, in flat black nondescript paint! And I say this with the highest praise! I absolutely love mine!
And when paired with a HeaterMeter DIY setup, it is perfect for me!