You should first get your ingredients prepared, because once you have made the roux, you can pretty much toss everything in, put a lid on the pan and walk away for 25 minutes.
I personally do not cut the salmon up, as I find it has a better texture if cooked whole then gently stirred in just prior to serving, but you can if you like.
Using fresh shrimp, of course is tastiest, but I find the frozen, ready to cook shrimp works great and saves a lot of work peeling and de-veining. So, frozen ready to cook shrimp saves about 10-15 minutes on the prep time.
MAKING THE ROUX: Place the 2 tablespoons of peanut oil in a large pot on medium high. Just as the oil releases a wisp of smoke, Reduce Heat to Low and use a fork to stir in the 2 tablespoons of whole wheat flour (as you would if you were making gravy). A white roux is ready when the flour begins to develop a toasty aroma. A darker roux is cooked longer while stirring constantly, until it reaches the desired color. It is said that Creole cooks prefer lighter to medium colored roux while Cajun cooks prefer it to be much darker. Make yours to your preference.
As soon as the flour and oil reaches the desired color, immediately start slowly stirring the liquid into the roux--only using a small portion of the broth/oyster sauce between stirrings (again, as you would with a gravy) to ensure an even consistency. (It really doesn't matter which you stir in first, though I usually stir in the oyster sauce since it is only one cup and easier to work with first.).
YOUR READY TO PUT IT ALL TOGETHER: Once the roux/broth mixture is ready, Increase Heat to High, add the rice, vegetables and spices. Stir the mix a few times as you wait for the entire pot to come to a rolling boil, just to make sure the rice doesn't stick to the bottom of the pan.
Once you have achieved a good solid rolling boil, Reduce Heat to Low, toss in your cleaned and de-veined shrimp, set the salmon on top and cover with lid.
At this point, you should not have to revisit the pot for 25 minutes, however, it seems irresistible not to check it every 15 minutes or so (especially the first time or two you make it) and that's ok, but remember, every time you lift the lid you add a couple of minutes to the required cooking time.
This is usually ready in 25 minutes, however it may require another 5 to 10 minutes if your range varies--or if you keep lifting the lid! (-:.
Once the rice is ready, the gumbo is ready. Take a large spoon and make a few slices through the salmon, then stir up the pot and serve.