Slice off top and bottom 1/8 inch of clementines. Cut away peel and pith, keeping fruit intact. Cut crosswise into 1/4-inch slices; place each in a 4-ounce timbale mold (jbprince.com) set on a rimmed baking sheet.
Mix gelatin and the 3 tablespoons water in a small bowl; let sit for 5 minutes until softened.
Combine white cranberry juice and the 1 cup water in a 1-quart measuring cup. Transfer 2 cups of the liquid to a small saucepan; heat over medium heat until simmering. Turn off heat. Add softened gelatin; stir until completely dissolved. Return hot mixture to measuring cup; stir in red cranberry juice.
Pour just enough of mixture into each mold to cover clementine slice. Refrigerate until set, about 10 minutes, then fill with remaining mixture. Refrigerate until firm, about 1 hour, or up to overnight.
To unmold, dip mold into warm water for about 10 seconds. Use fingers to pry edges of gelee away from mold. Invert mold onto dish; remove. Chill until ready to serve.