The candied orange I use is quite soft. You can candy your own or buy it in the store. If the one you buy is hard, rehydrate it in some sugar syrup.
Place the almond paste, candied orange, apricot puree, honey and Grand Marnier to the bowl of the stand mixer fitted with a paddle and mix until combined (you can also knead together by hand). You may need to adjust the amount of Grand Marnier depending on the texture of the paste. Roll out the almond paste mixture to 3/8-inch thick layer. I used some 3/8-inch thick rulers as guides so my almond paste would be rolled perfectly flat. You could use 2 wooden spoons. Let this sit overnight uncovered
Use an offset spatula to spread a 1/16-inch thick layer of Royal Icing on top of the rolled almond paste. Place this in the freezer until the Royal Icing sets, about 30 minutes, uncovered.
Use a sharp chef's knife coated with vegetable cooking spray to cut the Caillison d'Aix into diamond shapes. These are most often served after dessert.
To make royal icing: Combine the egg white and powdered sugar in a medium-size mixing bowl and whip with an electric mixer on medium speed until opaque and shiny, about 5 minutes. Add the lemon juice and continue whipping until completely incorporated, about 3 minutes. The lemon juice whitens the royal icing. The royal icing should be light, fluffy, and slightly stiff. You may need to adjust the consistency by adding more egg whites if the icing is too dry or more powdered sugar if it is too wet.
Place the royal icing in a small piping bag or paper cornet.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.