If using ready vacuum sealed frozen salmon (like the Ikea fillets I used), you don't need to season pre cooking. If your salmon isn't sealed, then sprinkle all over with salt and pepper, and place in sandwich bags.
Place the sealed salmon into a large pot of water to which the sous vide machine has been attached. If using sandwich bags, close the bag using the “water displacement” method: seal all but one corner of the bag, and place it in cold water. Make sure everything below the zip-line is covered by water. Then seal the rest of the bag. Alternately, you can use a vacuum sealer machine. If your bags are still floating, see notes.
Set sous vide to 130 F (54C) and turn it on for 70 minutes. When the timer goes off, remove salmon from the bags, pat dry, and if you haven't already, season with salt and pepper generously.
Heat the olive oil in a large skillet over medium high heat. Once very hot, add the salmon (it's now completely cooked, you just want to sear it for some texture) and sear on each side for 1 minute until golden brown.
Remove from the pan, squeeze some lemon juice on top of each fillet and enjoy plain or with whatever sauces/toppings you like.