Preheat the oven to 190℃/170℃ fan (375℉/340℉).
Arrange your courgette, aubergine and peppers well spread out on a large baking tray or roasting dish. Drizzle with 2 tbsp olive oil and season with the mixed herbs and a pinch of salt and pepper, to taste. Toss to coat.
Roast for 45-50 minutes, flipping half way through, until the vegetables are soft but not charred.
Set the vegetables aside to cool to room temperature.
Meanwhile, fry the halloumi. Slice the halloumi into 1cm slices. Heat 2 tsp of olive oil in a medium frying pan. Fry the halloumi until the slices are golden brown on both sides.
Set aside to cool.
Slice your ciabatta in half lengthways. Spread one half with the garlic mayo and one half with the pesto. Layer the pesto half with the aubergine, courgette and peppers. Sprinkle with the olives and top with the halloumi.
Top with the other half of the ciabatta and slice into 4-8 smaller sandwiches.
