To make the brine, place the salt and 3 litres of water in a large saucepan over a high heat, stirring until the salt dissolves. Cool to room temperature, then transfer to a 4 litre plastic container (or large enough to hold the pork shoulder) and place in the fridge to chill.
Immerse the pork shoulder in the chilled brine to cover completely. There maybe excess brine left over, so discard. Seal the container and place in the fridge for 24 hours.
An hour before roasting, remove the pork shoulder, discarding the brine. Pat dry all over with paper towel. Preheat the oven to 150°C (130°C fan-forced).
Heat the oil in a large heavy based casserole pot over a high heat. Add the pork and cook for 15 minutes, turning to brown all over. Pour in the cider and stock. Add the bay leaves, juniper berries, all spice and cinnamon. Cover with a piece of baking paper, then a tight fitting lid and transfer to the oven. Cook for 4 to 5 hours, until the pork is very tender and pulls away easily with a fork. Check after 3 hours in case the liquid has reduced to the point where the meat is catching on base, add a cup of water if needed.
Remove the meat to a large bowl, reserving the cooking juices. Shred the meat using fingers or two forks. Skim the excess fat from the surface of the cooking juices. Pour the remaining juices over the meat, tossing to coat.
To make the slaw, whisk together the dressing ingredients. Combine the fennel, cabbage and mint in a serving bowl. When ready to serve, pour over the dressing, tossing to mix.
Have ready the rolls, pulled pork and the bowl of fennel slaw. Allow guests to make up their own rolls.