Preheat: Preheat the oven to 180°C.
Prepare: Rinse the spinach and chop it finely. Crumble the feta cheese.
Stuff: Cut a pocket into the pork loin without cutting all the way through. Stuff it with the spinach and feta mixture.
Cook: Place the stuffed pork in the preheated oven and cook for about 50 minutes, or until the meat is thoroughly cooked.
Serve: Let the pork rest for a few minutes before slicing. Serve warm.