After a little fiddling, here's how I'm doing the jamaica now.
8 cups boiling water
1/2 cup sugar
1 cup dried hibiscus flowers
Juice of 3 small limes
Add the sugar and hibiscus to the boiling water and let it steep for at least 10 minutes, or till you remember to come back. Strain it and add the lime juice and chill. I also like it warm.