Preheat the oven to 200°C.
Mix couscous, cumin, spring onions, preserved lemons, coriander, and tomatoes in a bowl.
Slice the monkfish fillet into 1cm thick angled medallions.
Boil 180ml of water, add saffron, and remove from heat immediately.
Fold six large foil sheets in half to crease and then open them flat.
Stir 30ml of olive oil into the couscous mixture to coat the grains.
Add the saffron water to the couscous and stir to combine.
Grease the center of each foil sheet with oil and arrange sliced fennel on top.
Divide the couscous mixture equally over the fennel piles.
Place 2 to 3 slices of monkfish on top of each couscous portion.
Drizzle with remaining oil and season with salt and pepper.
Fold and seal two sides of each foil parcel tightly.
Ensure three sides are sealed and position parcels with the top opening angled up.
Pour approximately 45ml of water into each bag and seal the final edge.
Bake on trays for 15 to 20 minutes, swapping shelves halfway through.
Remove puffed parcels from the oven and place on warmed plates.
Toss cucumber, radishes, yogurt, lemon juice, sumac, and oil in a bowl with seasoning.
Serve the parcels closed to be opened at the table alongside the salad.