Rinse and pat dry the salmon, slice into two even portions. Salt and pepper the fish well.
Combine the harissa and garlic in a small bowl. If the paste is not very spreadable, add a glug of olive oil until it's a good consistency. Rub it all over the flesh side of the salmon.
If you are prepping this early huzzah for you -- stick that puppy in the fridge and let it marinate a few hours. At the least you should do 40 minutes, preferably 60. BUT if you are hangry and giving me stank eye right now I'll settle for 20.
(While the fish is getting flavor acquainted, prep toppings for the couscous and put them all in a bowl ready to mix in.)
Once the salmon has marinated for the chosen amount of time, take it out and remove excess marinade. Lay it with the skin side on paper towels to remove moisture so it can get super crispy.
Get two burners going. A small saucepan with 1 cup of salted water or stock set to boil for the couscous. And a large skillet on medium-high heat with your choice of cooking oil (high smoke point). Have your thyme sprigs and butter close by.
Once the oil is very hot, place your salmon skin side down into the pan and let it sizzle. Turn the heat down just a tad for even cooking. To stop that pesky curling that can happen, use a spatula and apply some gentle pressure for the first minute. This usually helps.
Quickly add a nub of butter and thyme sprigs to the pan. Using a spoon, baste the salmon allllll over with the melting butter and herbs, really get that aroma going. Leave it skin side down until it easily releases from the pan, 5-7 minutes.
Carefully flip the fish over to finish it off, 1-2 minutes.
Check the salmon for desired doneness, I prefer mine quite rare in the center so this is the timing I've given. If you want it cooked further simply leave it in the pan a few minutes more. Take off heat and give it all a squeeze of lemon.
Now give attention to the couscous! It should be steamy and fluffy because couscous is good like that and doesn't mind being ignored for a little while. Stir in a nub of butter and a small spoonful of harissa. Mix in all the toppings and use the last half of the lemon to squeeze on top.
For plating it looks very pretty serving it family style, with the salmon resting on the couscous and any leftover seeds/herbs on top. Sit back and relax with some wine and savor the great job you just did.