Empty bag of peanuts in a colander and rinse with cold water
Place peanuts in a slow cooker
Pour water over peanuts (allowing a few inches of water above the peanuts)
Pour salt over the peanuts and stir
Place lid on cooker and cook on HIGH for 6 to 8 hours
Stir occasionally (every hour or so)
Turn off cooker and carefully drain water
Stir the peanuts occasionally throughout the cooking process (every hour or so). Do not stir too often. After the peanuts have been cooking 6 hours, you will want to do a "taste-test" to test the texture and salt content.
The peanuts will continue to cook and absorb the salty water if you keep them in the water. So, you will need to drain the peanuts when they reach your desired taste and texture (usually between 6-8 hours). If you leave them in the salty water, they will absorb too much salt and the peanuts will become briny and virtually un-edible.
Note: Feel free to add to or take away the amount of salt you use. There is no true science to this. It is all a matter of taste and preference.