Peaches can be dried in the sun, but an oven works well too. Slice pitted peaches 1/8 inch thick, and arrange in a single layer on parchment-lined baking sheets. Bake at 150 degrees for 3 hours.
Preheat oven to 450 degrees. Bring 1 cup water to a boil in a small saucepan. Coarsely chop store-bought dried peaches if using. Add peaches to water; return to a boil. Remove from heat; let stand for 20 minutes. Remove peaches using a slotted spoon, and squeeze; reserve liquid.
Meanwhile, butterfly pork loin: Starting 3/4 inch from top of loin, make a horizontal cut into side, slicing through meat in short strokes and leaving about 1 inch intact at outer edge. Unfold meat (as if opening a book). Cut a vertical slit 3/4-inch deep at seam, and repeat to make a horizontal cut in the opposite direction. Pound to an even thickness with a meat mallet if needed.
Stir together a seasoning mixture of salt, pepper, and the cloves; sprinkle some over pork. Spread drained peaches over pork, leaving a 1-inch border on 1 short end. Roll up pork from short end to enclose filling. Tie together with kitchen twine to shape and hold in filling. Sprinkle with seasoning mixture; dust with flour. Place in a roasting pan, seam side down.
Bring reserved soaking liquid, the jam, and sugar to a boil in a small saucepan. Reduce heat; simmer for 1 minute.
Roast pork for 20 minutes. Reduce oven temperature to 350 degrees, and roast until an instant-read thermometer inserted into the center reaches 138 degrees, about 25 minutes more. Brush with glaze, and roast for 5 minutes more. Transfer pork to a platter; reserve juices in roasting pan. Let rest for 10 minutes. Brush with glaze again.
Pour accumulated pan juices into pot with glaze. Set roasting pan across 2 burners, and add remaining 1/4 cup water. Cook over medium-high heat, scraping up brown bits from bottom of pan. Add liquid and bits to glaze. Bring to a boil. Reduce heat, and simmer sauce for 1 minute. Stir in lemon juice.
Untie pork; cut into 1-inch-thick slices. Serve with sauce.