COMBINE flour and salt in large bowl. Beat shortening, sugar and vanilla in separate large bowl with electric mixer on medium speed until blended. Beat in egg yolks and orange juice. Gradually stir in flour mixture to form a soft dough. Divide dough into 4 equal pieces, shaping each into a disk. Wrap in plastic wrap. Chill 4 hours or overnight.
HEAT oven to 350 degrees F. Line baking sheets with parchment paper. Roll out dough, one piece at a time, to 1/4-inch thickness on floured surface.* Keep remaining dough chilled until ready to use. Cut out a total of 24 cookies, using the 2 largest cookie cutters 4 times each and the 8 remaining cookie cutters 2 times each. Bake on prepared baking sheets, 16 minutes for small cookies, 18 minutes for large cookies, or until edges begin to brown and centers are set. (Group similar size cookies on same baking sheet for even baking.) Carefully slide baked cookies on parchment paper onto work surface. Cookies may be fragile while warm. Cool completely.
STIR powdered sugar and meringue powder in large bowl until combined. Add water. Beat with electric mixer on medium-high speed until stiff peaks form, about 5 to 7 minutes. If necessary, add additional powdered sugar or water to reach the desired spreading consistency. (Keep frosting covered with damp cloth to prevent hardening.) Reserve one of the smallest size cookies for later use. Spread icing over remaining cookies, immediately topping with decorator sprinkles.
PLACE one of the largest size cookies on decorative platter to begin assembly. Spoon about 1 tablespoon remaining icing onto center of cookie. Repeat to stack additional 22 cookies on top, by decreasing size, rotating each cookie slightly to stagger points of stars. To complete decoration, hold reserved small cookie by its edges and coat both side with frosting. Decorate as desired. Stand upright on top of tree, securing with a small dab of icing. Let stand until icing is firm.
* When cutting out the largest size cookies, roll out dough on floured parchment paper. Cut with cookie cutter. Remove excess dough from around cookie cut outs. Lift parchment paper and place on baking sheet. Bake as directed above. ** Sets of graduated size cookie cutters and meringue powder are available at most craft stores with the cake decorating supplies