For poaching stock: In the bottom of a large oval slow cooker, combine the water, vegetable broth, white wine, lemon slices, shallots, capers, dill sprigs, salt, and peppercorns. Cover the slow cooker and cook on low for 4 to 8 hours.
For creamy dill sauce: Whisk together the Greek yogurt, sour cream, dill, parsley, apple cider vinegar, and House Seasoning in a small bowl. Adjust the seasoning with salt and pepper to taste, if desired. Cover the bowl and refrigerate the sauce for at least 2 hours, preferably longer, before serving.
Season the fleshy sides of the salmon fillets with salt and pepper to taste, and place them in the slow cooker, skin-side down. Cover the slow cooker and cook on high for 20 to 40 minutes, until the salmon is flaky and opaque, with the thickest part of the fillets measuring 145° on an instant-read thermometer. If your salmon fillets are thin or your slow cooker runs hot, check for doneness sooner. Serve the salmon fillets with the lemon wedges and Creamy Dill Sauce.