Preheat oven to 325°F. Butter 9x9x2-inch metal baking pan; line bottom and sides of pan with parchment paper, extending over sides. Butter parchment. Mix preserves and orange liqueur in small bowl; set aside.

Using electric mixer, beat 1 cup butter and sugar in large bowl until well blended. Beat in almond extract. Add flour and salt; beat just until blended. Transfer 1 cup of dough to another small bowl; add crumbled almond paste and mix with fingertips until small clumps form. Mix in 1/4 cup sliced almonds; set aside for topping.

Press remaining dough evenly onto bottom of prepared pan. Spread preserves mixture evenly over. Using fingertips, coarsely crumble topping over preserves, then sprinkle 1/4 cup almonds over. Press topping lightly into preserves.

Bake shortbread until top and crust edges are golden brown, about 1 hour. Cool completely in pan on rack. Using parchment paper as aid, lift shortbread from pan. Cut shortbread into 4 equal strips, then cut each strip crosswise into 8 small bar cookies. (Can be prepared ahead. Store in single layer in airtight container at room temperature up to 4 days or freeze up to 2 weeks.)