To make the tortillas, heat oven to 200C/180C fan/gas 6. Brush both sides of the tortillas with the oil, then cut into triangles with scissors. Arrange in a single layer on 1 or 2 baking sheets and bake for 7-8 mins. Remove, sprinkle with salt and set aside.
To make the guacamole, halve and stone the avocados, then spoon the flesh into a bowl. Pour over the lime juice and a sprinkle of salt, then crush with a potato masher until pureed but still chunky. Add onion, coriander, chillies and chipotle paste. Stir through and set aside until needed.
For the salsa, place the tomatoes, cut-side up, in a shallow baking tray. Season, and place under the grill until blackened, about 15 mins. Meanwhile, in a dry non-stick frying pan, blacken the chillies and garlic. Keep turning to darken on all sides, about 10 mins. When done, peel the garlic and place in a food processor. Place the chillies in a plastic bag to steam for a few mins, then peel, deseed and stem. Add the flesh to the food processor along with the tomatoes, onion, coriander, lime juice and chipotle paste. Season and pulse until chunky.