Make the pizza dough following pack instructions. Tip the dough onto a floured surface, flour your hands, then gently knead the dough for about 2 mins until fairly even, soft and bouncy. Return the dough to the bowl, cover with oiled cling film, then let it rise in a warm place until doubled in size (about 1 hr). While the dough proves, mix the passata and garlic in a bowl.
Heat oven to 240C/220C fan/gas 9 or as hot as it will go. Dust two baking sheets with flour. Split the dough into eight, then roll four balls into thin, rough circles. Lift onto the floured sheets. Smear a thin layer of the tomato sauce on top of each and scatter over the mozzarella and parmesan.
Halve each olive and put four halves, cut-side down on four pizzas – these are the spider bodies. Cut the rest of the olive halves into thin strips, then arrange on either side of the bodies to look like legs.
Put four pieces of salami or chorizo on the four remaining pizza bases. Cut the other pieces of salami into thin strips and use them to make the legs of the spiders. Add 2 capers to each spider for the eyes.
Bake each tray for 12 mins or until golden and crisp and the cheese is starting to brown.