Prepare the Slow Cooker:
Line the bottom and sides of a 5- to 6-quart slow cooker with two crisscrossed strips of aluminum foil for easy removal.
Spray the foil with non-stick cooking spray.

Layer the Waffles and Sausage:
Place the cut waffle pieces evenly in the bottom of the slow cooker.
Top with the cooked and crumbled beef sausage.

Mix the Egg Mixture:
In a medium bowl, whisk together the eggs, half-and-half, maple syrup, dried sage, salt, and black pepper until well combined.

Assemble the Casserole:
Pour the egg mixture evenly over the sausage and waffles in the slow cooker.
Sprinkle the shredded cheddar cheese on top.

Cook:
Cover the slow cooker with its lid.
Cook on low for 5 to 6 hours, or until the eggs are set and the casserole is cooked through.

Serve:
Carefully lift the casserole out of the slow cooker using the foil handles.
Slice and serve warm.