Cook macaroni according to the package's directions. Drain and place in slow cooker.
Cut cheese block into cubes and place on top of noodles. Add shredded cheddar cheese, butter, and the half and half.
Cook on low for 1 hour or on high for 30 minutes or until cheese is nice and melted. Remove lid and stir well until all the melted cheese has coated the noodles. Cook for an addition 15-20 minutes.