I have extremely limited experience with Chinook on the fly...just the one I recently caught casting a Krystal Flash Clouser using an LC-13 shooting head off a Point Dalco ledge. However, in all fairness, that was also my first attempt targeting them. Conventional wisdom puts Chinook deep (125ft+) at the Clay Banks around Point Defiance during an incoming tide which is why that place looks like a parking lot. I expect to find them more toward the surface at dawn's light around points of land such as Point Evans in under 60 feet of water. Maybe I'm wrong, but I'll have fun proving it.
A very effective fly has been developed and is gaining popularity among gear fishermen here as a deep trolling lure off a downrigger (Grand Slam Bucktail) which, for all practical purposes, is a Krystal Flash tube fly between 4'" and 6" with colors to emulate Anchovy and Herring. Maybe I'm naive, but I would think a Clouser, or something similar to the aforementioned GSB, casted and retrieved on a quick sinking line in appropriate structure, would be equally effective. Though I could be wrong, I think there are times of the day when the Chinook can be found in shallower waters. At least that's what I'm betting on. Hopefully, Topwater can provide better insight. Like I said, I'm new to fishing the Kings on a fly and my thinking may be more wishful than factual.