Boil the cider in a small saucepan until it's reduced by half (½ cup). Remove from the heat and stir in the butter, honey, salt and black pepper to taste.
Put the vegetables in the slow cooker and pour the cider mixture over. Stir to coat.
Cook on high for 3 hours or on low for 6 hours. Serve warm sprinkled with fresh thyme.
Notes
Check the vegetables during the last 15 minutes of cooking. If you'd like a thicker glaze, remove the lid and cook on high for 10 - 15 minutes to reduce the liquid a bit more.
To make your vegetables a little dressier, sprinkle on some toasted chopped nuts like pecans or walnuts, and grated Gruyere or Parmesan cheese.