Peel the carrots and slice into 1 1/2-inch chunks. Set aside.
In a small saucepan or a microwave-safe bowl, melt the butter. Pour into the bottom of a 4-quart or larger slow cooker. Add the honey, orange zest, and salt, then stir to combine. Add the carrots and stir to coat.
Cover the slow cooker and cook on low for 4-6 hours or high for 2-3 hours until tender, stirring once halfway through. Serve warm, garnished with parsley.
Notes
TO MAKE AHEAD: Carrots can be peeled and sliced up to 2 days in advance.
TO STORE: Store leftovers in the refrigerator—the butter will harden on the outside but melt again and be delicious when the leftover carrots are reheated.