Bring a large stockpot of water to a boil, and season with 1 tablespoon of kosher salt. Once the water comes to a boil, remove it from the heat. Immerse two of the crabs into the water for 5-10 minutes until the crabs are warmed through. Remove the crabs from the water and set aside to drain. Bring the water to another boil and repeat with the remaining crabs.

Clean the crabs while the other two crabs are warming in the hot water. Crack the legs with the back of a heavy knife. Serve on a platter with fresh dill leaves, parsley, and sliced lemons and limes.

In a small saucepan over medium heat, melt the butter. Reduce the heat to low and skim the foam from the butter. Stir in the Old Bay Seasoning and the lemon juice. In a small bowl, mix the ketchup with the prepared horseradish. Serve the flavored butter and cocktail sauce alongside the crab.