If fish is frozen quickly in special freezers, the water inside each cell makes smaller crystals that keep from breaking open the cell and killing the taste and texture. Freezing slowly makes bigger crystals. BTW, Salmon is my faaaavorite fish ever. I could eat it every day
I don't know of how to cook it after it's been frozen slowly, but here's how I usually cook it:
1 - Rinse off salmon
2 - Wrap in tin foil, allowing room for the fish to expand
3 - Brush a mix of butter, lemon, and white wine
4 - add whatever herbs you see fit
5 - Bake for a few minutes
6 - Add a bit more wine/butter
7 - Continue cooking (I think it's 10 minutes per 1" thickness)
When it's done I usually serve it with a few of those little red potatoes (simply boiled) and veggies. I usually cook the veggies with garlic since my bf loves it.