In a mixing bowl, combine the tapioca starch with ¼ cup of the coconut milk until smooth. In a small saucepan, heat the remaining coconut milk over low heat until it begins to bubble. Whisk in the starch mixture to the warm coconut milk and stir continuously until mixture begins to thicken. Once mixture begins to thicken, remove immediately and whisk in the juice. You may also whisk in pulp if desired. Transfer mixture to popsicle mold or individual cups with a straw inserted in the center. Place in freezer for 4 hours.