In a bowl, combine sunflower oil, soy sauce, lemon juice, sea salt, freshly ground pepper, paprika, oregano, and honey with minced garlic.
Place the pork loin on a cutting board. Hold the knife parallel to the cutting board and about 1-2 inches from the bottom edge of the pork loin. Make shallow, evenly spaced cuts across the entire length of the pork loin, stopping about 1/2 inch from the far edge. Open the pork loin, laying it flat with the “unzipped” side facing up.
Place the open pork loin between two sheets of plastic wrap and using a meat mallet gently pound the pork loin to an even thickness, about 1/2 to 3/4 inch thick.
Coat the meat with the prepared baste, carefully roll it back to its original shape and let it sit at room temperature for an hour.
Cut the potatoes into thick rounds and add them to a bowl. Slice the onion and add it on top.
Season with sea salt, paprika, and oregano. Drizzle in the sunflower oil and toss them well to evenly coat and infuse them with flavour.
Unroll the marinated meat and fill it with roasted red peppers, grated mozzarella and pre-cooked smoked ham slices.
Roll the pork loin up tightly, enclosing the stuffing and secure the roll with kitchen twine or butcher’s twine at regular intervals.
Place the stuffed pork loin in the middle of the tray, surrounded by the evenly spread potato and onion mixture. Brush the meat with the prepared baste.
Cover the roasting pan with aluminium foil and place it in the oven preheated to 190°C (375°F) fan for an initial 45 minutes.
Remove the foil, brush the meat again for a final browning and return the tray to the oven for 15-20 minutes
Once out of the oven, brush the stuffed pork loin with baste and let it cool slightly before slicing into it.
Serve the stuffed pork loin with the roasted potato and onion mix.