2 cups mixed raspberries, blackberries and blueberries, plus more for garnish
In a large heatproof bowl, combine the hibiscus, zest and thyme. Add 4 cups of boiling water and let stand for 15 minutes, stirring occasionally, until the liquid is rosy pink.
Strain the liquid into a microwave-safe pitcher, stopping when you reach the grit at the bottom. Measure out 3 cups. Pour 1 cup into a small bowl and sprinkle the gelatin over it. Let stand until softened, about 5 minutes. Scrape the softened gelatin into the pitcher and stir in the sugar and lemon juice. Microwave the mixture for 10 to 15 seconds, until the gelatin is melted and the sugar is dissolved. Refrigerate until chilled but not set, about 30 minutes.
Pour the mixture into eight 1/2-cup molds and refrigerate until partially set, about 30 minutes. Poke the berries into the gelatin and refrigerate until completely firm, at least 4 hours and preferably overnight.
Dip one mold at a time in a pan of hot water for 5 seconds. Invert a plate over the mold and invert the mold and plate. Lift off the mold. Serve.
The molds can be refrigerated for up to 4 days.
Hibiscus flowers are available at health food stores and tea shops.