-Add the diced celery, carrots, onions, and potatoes into the slow cooker. Season with salt, pepper, and thyme. Stir to combine.
-Add the chicken stock, mushroom soup, clams (with their liquid), and butter. Cover partially (I like to vent the cover with a wooden spoon) and cook on high for approximately 4-5 hours.
*Note - The venting of the cover will help the chowder to reduce and help the flavor intensify.
-After 4-5 hours, reduce the heat to low, add in the chopped shrimp and the seafood seasoning. Stir. Continue to cook (covered and vented) for an additional 1-2 hours.
-In a small bowl, whisk together the half-and-half and the corn starch. Pour the corn starch mixture into the chowder and stir occasionally. This mixture will thicken the chowder as it heats.
-Right before serving, stir in the lemon juice.
-To serve, ladle the chowder into bowls or mugs and top with oyster crackers, if desired.