In a large stockpot, dissolve 1/2 cup kosher salt in 2 gallons water. Add raw peanuts, and place a plate or bowl on top to keep them submerged. Soak 8 hours or overnight. Skip this step for green peanuts.
Drain soaked peanuts and return them to the pot. Add 2 fresh gallons water and the remaining 1 cup kosher salt. Bring to a boil, then reduce heat to low and cover. Simmer gently, adding water as needed to keep peanuts submerged.
Cook until soft, briny and flavorful, about 5 to 8 hours for raw peanuts or 2 to 3 hours for green peanuts. Start tasting early. A perfect boiled peanut should feel tender all the way through, never crunchy in the center.
After about 3 hours for raw peanuts (or 1 hour for green peanuts), taste and adjust. Want more salt? Add in 1/4-cup increments. Too salty? Add fresh water.
When tender, remove from heat and let cool in the cooking liquid for about 1 hour (20 to 30 minutes for green peanuts). This extra soak deepens flavor and gives them that roadside-stand taste.
Drain and enjoy warm, room temperature or straight from the fridge. Store refrigerated for up to 10 days, or freeze for several months.