Score the skin of the pork (if it has skin) in a crossed pattern, cutting through the skin but not deeper into the pork itself. Pat dry the pork.
Grind the caraway seeds with a pestle and mortar or chop them as finely as you can with a knife. Grate or crush the garlic. Mix both together with ½teaspoon salt, the pepper and oil into a paste then rub the mixture all over the pork, both into the scores in the skin and over the exposed pork.
Peel and roughly dice the onion, carrot and parsnip. Place the pork, skin side down, in a Dutch oven or other roasting dish with a lid and place the chopped vegetables around the pork.
Pour most of the beer over both the pork and vegetables then roast for around 45 minutes, covered.
Turn over the pork so the skin side is up and pour over the remaining beer. Rub the extra salt over the skin then return to the oven and roast for another 1 ¼hour, approximately, uncovered, until it is starting to look crisp on top (and meat thermometer gives an internal reading of 165F/74C).
Once the pork is cooked, place the meat on a tray and finish off under an overhead broiler/grill to crisp skin slightly more, if needed, then cover to rest before cutting. Keep an eye on it as the skin crisps as it may quickly turn from crisp to burnt.
As the pork is resting, make the gravy. Strain the beer mixture from the roasting dish. Once it has settled a minute, starin off the fat from the top. Melt the butter in a pan and add the flour and stir to form a paste. Add the strained beet and stir to reduce slightly and thicken a bit.
Remove the pork skin and serve in chunks alongside slices of pork, topped with the beer gravy with your choice of sides.
A slightly larger or smaller piece of pork is fine, it just may take a little longer or shorter time to cook. And if much larger, you will need additional salt/caraway/garlic rub as well.