Begin by making oversized decorative ice cubes. Combine grape juice and filtered water in an easy-to-pour pitcher or decanter. Arrange silicone molds on a sheet pan that will slide into your freezer with ease.
In each mold, arrange a combination of fresh cranberries, raspberries, pomegranate seeds, sage leaves and rosemary sprigs, filling garnishes to the top. Slowly add liquid to the tops and freeze, ideally overnight.
The day before your event, begin by making your hibiscus tea. In a large stockpot, bring water to a boil, remove from heat then add hibiscus tea bags to steep. Remove bags after 15 minutes, stir in stevia and let cool completely.
After tea has cooled, combine tea with remaining juices, excluding the canned ginger ale. Let chill until ice cold, preferably overnight to allow flavors to develop.
To serve, add hibiscus punch to a large punch bowl and stir in canned ginger ale. Finish with decorative ice cubes and serve.