To large saucepan, add all ingredients and, while stirring frequently, bring to a hard simmer over medium-high heat. Turn heat to low and allow mixture to simmer gently for 30 minutes. Remove saucepan from heat and strain mulled juice into heatproof bowl or pitcher. Discard solids.

To serve, divide mulled mocktail among mugs and garnish with an additional orange slice, if desired. Serve while hot.

Any leftover mulled mocktail may be refrigerated for up to 4 days and reheated gently before serving.