Peel and seed the squash and cut into about 1-inch cubes.
Combine the fresh squash cubes, onion, chicken stock, apple cider and seasonings in a 6-quart slow cooker. Cook on low for 8 hours.
Remove lid and add the cream cheese. Blend the soup with an immersion blender until smooth.
While the soup is cooking, cube the bread and toss with the melted butter and remaining 1/4 teaspoon of salt.
Spread in an even layer on a sheet pan lined with a silicone baking mat or parchment paper.
Broil on high until both sides of the bread cubes are nicely browned. Remove from the oven to cool.
Serve the soup topped with the cinnamon bread croutons.