Aug 28, 2016· Once that is jammed under the flange, and the flange is level, the next step is to mix the dry-pack mortar. As a side note, 3/4 in. would be the thinnest I would ever install dry-pack, I usually aim for the thinnest areas to be roughly 1 1/4 in. thick and try not to go greater 2 in. thick.