Prepare the mold: Lightly grease a non-stick square mold with vegetable oil on the bottom and sides. Wipe excess oil from the bottom to prevent sticking.
Make the lower layer: In a bowl, combine 1 cup finely ground unsweetened coconut, 1 cup finely ground pistachios, 1/2 cup fine sugar, and 1/2 cup honey. Add 1 teaspoon orange blossom water and 1 teaspoon rose water. Mix well by hand until a soft, homogeneous dough forms that can be shaped.
Form the lower layer in the mold: Spread the dough evenly in the greased mold using your hands or a tool to smooth and press it firmly and evenly over the entire bottom. Cover and refrigerate for about 2 hours.
Prepare the upper layer: In another bowl, mix 2 cups finely ground unsweetened coconut, 1/2 cup fine sugar, 1/2 teaspoon ground mastic with sugar, and 1 cup condensed milk. Stir with a spoon until the mixture thickens and becomes consistent.
Add the upper layer: Spread the coconut mixture evenly over the chilled pistachio layer in the mold.
Chill overnight: Cover the mold with foil and refrigerate the dessert overnight (about 8-12 hours) to allow the coconut to solidify and the dessert to set.
Decorate and cut: Before serving, optionally smooth the surface with a flat heavy tool covered with butter paper. Prepare a sugar mixture by mixing 1 tablespoon fine sugar and 1 teaspoon ground mastic with sugar. Sprinkle this mixture evenly over the surface using a brush or sprinkler. Decorate with pistachio nuts scattered evenly. Cut into neat squares and serve.