Combine sweet potatoes, apple, cranberries, orange juice, brown sugar, cinnamon, nutmeg, and salt in a slow cooker and stir. Add melted butter and stir again.
Cook on High for 2 hours, stirring every hour to redistribute liquid. Reduce heat to Low and continue cooking and stirring until sweet potatoes are tender, 2 to 4 hours more.
Set slow cooker to Warm setting until ready to serve. Serve garnished with pecans.
