While your slow cooker is within reach, whisk together the paprika, salt, garlic powder, onion powder, black pepper, and red pepper flakes in a small bowl—this creates an even seasoning distribution that won't clump when sprinkled. Meanwhile, zest both lemons directly into a small bowl, then juice them and set the juice aside separately. I find doing all the prep work at once keeps the cooking process streamlined and prevents any overlooked ingredients.

Place the boneless, skinless chicken thighs into your slow cooker in a relatively even layer. Sprinkle the spice blend from Step 1 evenly over all the chicken pieces, then distribute the minced garlic and lemon zest across the top. Pour the fresh lemon juice over everything, then dot the surface with the salted butter in small pieces. The butter will melt during cooking and create a rich, lemony sauce that coats the chicken beautifully.

Cover your slow cooker and cook on low for 4 to 5 hours, or on high for 3 hours, until the chicken reaches an internal temperature of 172°F (74°C) when checked with a meat thermometer at the thickest part. I prefer the low-and-slow method as it keeps the chicken incredibly moist and allows the lemon and garlic flavors to meld beautifully throughout the meat.

Transfer the cooked chicken to a serving platter and drizzle generously with the cooking liquid from the slow cooker—this lemony sauce is liquid gold. Garnish with the fresh chopped parsley and serve immediately alongside your favorite sides like rice, roasted vegetables, or crusty bread to soak up every drop of that incredible sauce.