Fill a large pot with water and squeeze in the juice of half a lemon, then add the remaining lemon slices, minced garlic, bay leaf, and a generous sprinkle of salt. Heat the pot over medium-high heat until it reaches a rolling boil (5-7 minutes).

Once the water is boiling vigorously, carefully add the peeled and deveined shrimp. Cook them for 2-3 minutes until they turn pink and opaque, stirring occasionally.

Immediately drain the cooked shrimp and transfer them to a large bowl filled with ice water for 3-5 minutes to halt the cooking process.

In a mixing bowl, combine the ketchup, prepared horseradish, freshly squeezed lemon juice, Worcestershire sauce, and hot sauce if desired. Stir together and season with salt and pepper to taste.

Arrange the chilled shrimp on a decorative platter. Garnish with lemon wedges and fresh parsley. Serve the cocktail sauce in small bowls.