Slice the aubergine in half lengthways. Lay the aubergine flesh side up on a baking tray, slice diagonally 1 cm deep into the aubergine in a criss cross pattern. In a bowl, mix half of the harissa spice with 1 tbsp olive oil and spread over the aubergine. Sprinkle over a pinch of sea salt. Place in the oven for 20-25 mins until soft.