A Mortar mixing tray is this:
They are approximately 2' x 3' x 7" deep. As you can see, I grow my Sarracenia in these undrained and in pure sphagnum peat moss. I typically flood them about every 2 or 3 days in the dry summer months. In winter Mother Nature floods them for me.
When it comes to Sarracenia, its pretty dang hard to overwater them.