To make hibiscus simple syrup (can be ahead of time)
Combine 1 cup water, 1 cup sugar and ¼ cup dried hibiscus flowers in a small pan. Bring to a boil, reduce the heat to a simmer and simmer for around 10 minutes until the sugar has dissolved and the liquid is a deep pink/red color (it may be darker depending on the hibiscus). Remove from heat and allow to cool.
To make hibiscus mezcal sour
Put the mezcal, lime juice and hibiscus simple syrup in a cocktail shaker along with plenty of ice. Shake for a minute until the drink is well chilled. Strain into a glass either over ice or straight up.
You can store the hibiscus simple syrup for a week or two in the refrigerator and use in many drinks in place of regular simple syrup for a splash of color and gently floral-tart flavor.