1. Preheat the oven to 220ºC, gas mark 6. Remove the string from the pork and pat the skin with kitchen paper until it is completely dry. Scrunch up a large sheet of foil to create a thick base in a roasting tin then lay the pork on top, skin-side up. Pound the salt and fennel seeds together in a pestle and mortar until fine, then rub half into the pork skin, reserving the remainder for later.
2. Roast the pork for 1 hour, then remove from the oven and leave to cool slightly. Turn the oven down to 180ºC, gas mark 4. Using a sharp knife, carefully remove the skin and return to the roasting tray. Wrap the meat in foil, lay next to the skin and return to the oven for 3 hours.
3. Meanwhile make the flatbreads. Combine the flour, baking powder and salt into a bowl and make a well in the middle. Pour in the yogurt then stir with a fork to combine. When the mixture forms a rough dough, turn out onto a lightly floured work surface and knead to form a smooth ball.
4. Divide the dough into 12 equal pieces and roll out into thin rounds, about 15cm in diameter.
5. Heat a large dry frying pan over a medium-high heat. Cook the flatbreads a couple at a time for 1-2 minutes on each side until golden. Wrap the finished breads in foil and set aside.
6. For the sauce, combine the garlic, vinegar, capers, mustard and anchovies in a large bowl. Pile the herbs up on a chopping board and roughly chop, adding a little oil as you go to combine everything. Scrape into the bowl, then stir in the remaining oil and season to taste.
7. Roughly shred the pork with 2 forks and season with the remaining fennel salt. Crush the crackling into small pieces using the end of a rolling pin. Meanwhile reheat the flatbreads in the oven for a few minutes. To serve, divide the pork between the flatbreads and top with pieces of crackling, a spoonful of the sauce and a few leaves of watercress.