Lightly grease the liner of the slow cooker with coconut oil or nonstick spray for greasing. Line 2 large baking sheets with parchment paper or silicone mats and set aside.: Warm, faintly tropical notes will rise from the coconut oil as you rub it over the liner, and that scent tells you the surface is ready to release the candy later. Press the spray or oil into the cooker with a paper towel so you leave a thin film rather than globs. When you lay down the parchment, you create two clean staging areas that will make the final unmolding effortless. A common slip is skimping on greasing, which leads to tearing when you remove clusters, so take the extra thirty seconds to coat the liner thoroughly.
Spread 16 ounces dry roasted, salted peanuts out on the bottom of the slow cooker. If your nuts are not salted, sprinkle with 1/2 teaspoon of salt. Sprinkle the 1 cup dark chocolate chips, 1 cup peanut butter chips, 1 cup white chocolate chips, and 1 cup semi-sweet chocolate chips over the nuts.: When you scatter the peanuts evenly across the bottom, you should hear a faint rustle and see a uniform layer that lets the chocolate touch nut on all sides. The visual of colorful chips over the tan nuts is satisfying, and it signals even melting. If your nuts were unsalted, that half teaspoon of salt brightens everything, making flavors pop. Avoid piling chips in one spot, which can cause uneven melting and clumps that are hard to mix through.
Place a clean kitchen towel over the liner of the slow cooker and then place the lid on the slow cooker. Turn the slow cooker to LOW heat. Cook on low heat for 1 hour. Remove the lid and towel and give the mixture a stir. If needed, recover and continue to cook for 15-30 minutes until the chocolate is fully melted.: You will hear a soft sizzling whisper as the chips begin to relax and merge, and the steam trapped under the towel softens the chocolate without scorching. After an hour the mixture should look glossy with partially melted chips; stirring helps coax the rest to melt evenly. If it still has stubborn pieces, recover and allow fifteen to thirty more minutes, checking every ten minutes. A common mistake is turning the heat up, which can cause the chocolate to seize and become grainy, so resist the urge and be patient.
After 15 minutes, remove the lid again, and mix the nuts evenly into the melted chocolate until everything is nice and combined and the nuts are fully coated in the chocolate mixture.: Expect a satisfyingly thick, coat like texture as you fold the nuts into the warm chocolate pool, and you may notice strands of chocolate stretching as you stir. The act of mixing distributes heat and ensures each peanut gets enveloped. Look for a glossy sheen and uniform color as cues that it is ready. If you see dry pockets of chips or oil separation, keep stirring slowly and allow another short period in the cooker. Avoid over mixing aggressively, which can break nuts or incorporate air that dulls the finish.
Using a small cookie scoop or two small spoons, scoop 1-2 tablespoons of the crockpot candy into small mounds onto the prepared baking sheets. Allow the candy to set up and the chocolate to harden at room temperature for an hour or so, or speed up the process by placing the trays into the refrigerator for 10-15 minutes.: As you scoop, you will notice the clusters hold their shape, glossy edges cooling to matte centers, and the smell of warm chocolate will be comforting. The mound should retain texture but not be runny; if it spreads too much, the mix was too hot, so chill briefly before continuing. Speed chilling is handy when you need the trays to set quickly, though very rapid cooling can sometimes add condensation if your kitchen is humid. A typical error is making scoops too large, which then take excessively long to set and can glaciate the centers.
Remove the candy from the silicone mats or parchment paper and store them for up to 14 days in an airtight container in the refrigerator or a cool, dry spot.: The finished clusters should have a clean underside and firm bite when cooled, and moving them carefully off the parchment preserves their shape. Store in an airtight container to protect them from absorbing fridge odors, and separate layers with parchment if stacking. In warmer homes, refrigeration keeps them intact, but remember that chilling can slightly dull aromas, so bring to room temperature briefly before serving for best flavor. A common oversight is leaving them exposed to ambient humidity, which can make them sticky.