If u plan on not keeping sand for a couple days so they can get accustomed to your lighting schedule & u can observe them more closely so they won't stay in the sand then they may be ok. I wouldn't let them go more then that without sand.
Personally, I would put a container of sand in the qt. To me it would be a little less stressful & imo stress is the biggest killer in leopards the first couple days to week.
If u are going to qt them u need to have a established qt tank with liverock & preferably atleast a container with sand. They do best in a reef tank & that is how the qt needs to be set up. If not, they are better off going straight to the dt.
I have four leopards & they all went straight to the dt. I have qted every fish the last five or so years except leopards. They need the reef like qt, the regular old qt with pvc fittings & such they will have a slim chance to make it imo