I do a nice poached salmon with white wine and fish stock, bay leaves, lemon juice, and parsley, but I just add it all to a fish kettle, bring it to the boil, turn off the heat and leave it for 4 hours, but it's kind of fancy and uses a whole fish, you could easily adapt it for fillets.
Yes you could do the fillets in a slow cooker, but tbh they won't take more than half an hour to cook, so i'd be inclined to just do them in a lidded frying pan type thing on the hob, otherwise the fillets might all break up?
Quick hollandaise sauce:
Ingredients - makes about ½ pint/300ml
2 egg yolks Fresh lemon juice 250g unsalted butter, melted 1 tablsp cold water Salt pinch Cayenne pepper
In a Blender put 2 egg yolks, squeeze in about 1tablespoon of fresh lemon juice and add 1 tablespoon of cold water. Put the lid on the blender ( or youll have a re-decorated kitchen - take it from one who knows!) and turn it on. Open the plug in the middle and with the blender still going, slowly pour in the hot melted butter. Whizz until thick. For a lighter sauce, add a little egg white to the yolks. Season to taste with Cayenne, Salt and more lemon juice if desired.
For parsley sauce, one the white sauce is cooked, add lots of chopped parsley, a drizzle of cream and a swueeze of lemon juice. You will probably want to halve the white sauce recipe too as you won't need much parsley sauce. You can thin it down with more milk or cream if it is too thick, to get it how you want it.