Crystal Caverns

''You finally reach the end of the underground passageway that leads from the Sith Palace to the Crystal Caverns. You've passed the tests and are proceeding to the caverns to find crystals for a lightsaber of your own. You have the lightsaber parts with you and you've just given away your training lightsaber. You see the marks in the cavern walls closest to the entrance and know that many apprentices had taken the ones closest; an easy task. As you walk deeper and deeper into the caverns, you reminisce about how you'd gotten to this point. Excited about customizing and making your own lightsaber, you hurry on into the gloom.''

This is where Apprentices who've passed the test make their lightsabers, whether double-sided or not.