Cut a sheet of parchment paper to fit the bottom of a half sheet pan (i.e., baking sheet). Place the parchment paper on the counter and roll out the block of refrigerated dough to cover the entire sheet of parchment paper. Start by rolling the dough out on the counter and when it covers most of the parchment paper, transfer it to the baking sheet and finish rolling. Run your hands over the dough to feel that it is level. Gently press out any large air bubbles. Trim the edges of the dough when in the pan so there is only dough on the bottom (i.e., no dough on the sides of the pan).
If the dough has softened a lot (i.e., is not cool to the touch), put the pan in the fridge for a few minutes so the dough can harden again.
Cover the dough and pan with a larger sheet of parchment paper, and fill with raw rice.
Bake in the oven for approximately 15 minutes. The dough should no longer look raw, but it should also not have much color yet (i.e., it should not be golden brown). The dough will be cooked a second time after the caramel topping is added and it will finish baking at that time. Remove shortbread cookie from the oven, place on a cooling rack until the caramel nut topping is finished, and remove the parchment paper and rice. Try to avoid spilling any rice as you are removing it. If rice falls onto the cookie, VERY CAREFULLY remove the rice. The pan will be hot so don’t get burned. Increase the oven temperature to 350°F/177°C.