Do not create holes, if you use chitubox, this software may automatically create a hole for the removal of resin. In your slicer software you need to create support, you can put the shell to 45 degrees. Personally I use Lycheeslicer, it is a bit less simple than chitubox but it is very good. However you can stay on chitubox but prefer prints with support for the shells you will have less problem. You can even put a single large support on a slice for it to work , it must have a large enough base to support suction when lifting the tray, I will try to make you screenshots.