Place cucumber slices in a colander and sprinkle lightly with salt. Let it sweat while you prepare the fish.
Rinse and pat dry the salmon fillets. Place skin-side down on a foil-lined baking sheet (makes for easy pan cleanup). Do not grease the foil. You want the skin to stick to it when you remove the fillets.
Preheat your oven to 375 degrees F. Season the fillets with salt and pepper. Dust with blackened seasoning. [Blackened seasoning is a mix of black pepper, cayenne pepper and crushed red pepper flakes among other herbs. If you like it extra spicy, double the amount of seasoning.]
Place skins on garlic cloves on a piece of foil. Drizzle lightly with olive oil. Wrap up the foil into a tight pouch. Place the pouch alongside the salmon. Roast the salmon and garlic for about 20 minutes or until fish easily flakes. You can also grill the fish if you prefer, it’ll taste even better.
In a small bowl, mix mayo, olive oil and lemon juice. Squeeze the cooled garlic pulp from the skins and combine with the mayo (can be done in a food processor). Season the garlic aioli with salt and pepper. Refrigerate until ready to serve.
Cut focaccia bread in half or quarter it for smaller portions and then slice creating a pocket. Smear inside focaccia generously with garlic aioli. Add salmon fillet. Top salmon with cucumber slices; sprinkle with fresh dill.