Mash the garlic, salt and cumin in a mortar or on a good board and mash them into a paste. Put the mashed garlic and cumin in a mixing jug. Add the vinegar and olive oil and whisk together to make a dressing.
Now to assemble, layer the bread, tomatoes, cucumbers, peppers, onion, grapes and herbs. Drizzle the dressing over the salad. The salad will become tossed as it is served. The bread will soak up all the delicious dressing.