1 Place the pork into a large roasting tin. 2  Tuck the two onion halves under the meat, this will help keep the meat upright as well as adding flavour to the meat. 3  Cook for 1 hour and 40 minutes. 4  If you are using a larger or smaller joint then cook for 25 minutes per 450g/1lb, plus add on a further 25 minutes. Sprinkle with salt, again make sure it is down into the slits. 2  Place the pork into a large roasting tin. 3  Tuck the two onion halves under the meat, this will help keep the meat upright as well as adding flavour to the meat. 4  Cook for 1 hour and 40 minutes.