Cream butter, sugar, and almond paste until pale; add eggs one at a time, then almond extract. Mix flour and salt, then stir in just until combined.

Divide batter into three bowls. Color one green, one red, and leave the third plain. Spread each into a parchment-lined 9x13-inch pan. Bake at 350°F for 10 to 12 minutes until set. Cool completely.

Invert the green layer onto wax paper and spread with half the preserves. Top with the plain layer, spread with remaining preserves, then add the red layer on top.

Wrap the stack in plastic, place a cutting board on top, and weight with heavy cans. Chill 8 hours or overnight.

Melt chocolate with oil and spread over the top of the chilled block. Let cool at room temperature 5 minutes, then refrigerate until the chocolate is firm.

Trim the edges and cut into bars. Wipe the knife between slices for clean lines.