Use a crockpot on high heat or a oven slow cooker setting on high heat.
Season the pork loin roast with kosher salt. Heat a skillet or cast iron skillet to medium high heat and add the olive oil. Sear the roast on all sides until browned, about five minutes.
Next, place the pork loin roast in a slow cooker, Crockpot or cooking pan. Season the roast with Herbs de Provence. Add the cider, brandy and apple and cover the roast with the lid or if using a cooking pan, cover tightly with foil.
Allow the roast to slow cook for 4 to 5 hours on high in the slow cooker or oven on the high slow cook setting.
The pork should be fork tender after 4 to 5 hours. Move the pork roast to a serving platter and strain the pan juices into a large measuring cup, yielding to 2 - 2 1/2 cups. Toss the apple solids.
To make the gravy, melt 2 tablespoons of butter and mix in 2 tablespoons of flour to make a roux. Slowly add in 2 cups of the pan cider juices and the cooking sherry and stir until slightly thickened. Use the remaining juices to thin the gravy if necessary.