The day before you're ready to cook, take the pork loin from its package, pat dry, and rub with salt (and any optional spices). Place on a wire rack laid inside a rimmed baking sheet and refrigerate, uncovered, for at least 8 and up to 24 hours.
Bring the pork out of the fridge 30 to 60 minutes before you're ready to cook. Heat the oven to 350°F.
Place roast in oven and cook for about 15 minutes per pound, until a meat thermometer registers 145°F. Remove from oven and rest 30 minutes before slicing and serving.