Why do I need to put sablé dough in the fridge?
Therre are actually two things that happen during the refrigerated rest period:


Obviously, the dough is cooled, which firms up the butter, making it easier to roll out without having it fall apart.
The starch granules absorb water, making the dough more cohesive, improving its texture, and making it easier to work


See:  What does an overnight chill do to cookie dough, that a 4 hour chill doesn&#39;t?