In a bowl mix wholemeal flour, yeast, linseeds, salt and water with a rubber spatula. Cover bowl with plastic wrap and then a tea towel. Set aside until doubled in size, which will take a couple of hours at the most.
Pre heat oven to 200 degrees. Flour your working surface and get a good ball of dough from the bowl, roll out to a size you're happy with. Top the pizza with some passata, then add your pizza ingredients. Finish with a sprinkle of sea salt. Put in oven and cook until cheese has melted and the edges of the dough are starting to go golden. To make the base crisp put the oven tray on a gas stove top to finish.