Bonnie that setting is wonderful.
My smallest liner pond is about 18" deep in the shallow end created for Helvola and 22" deep in the deeper end. I did put clay soil on top of the liner and plant right into it. I did this with the bigger one too. Perry's Baby Red, Hermine and Charlie's Choice are in the bigger one. The biggest one does not have the dirt on the bottom yet. DH doesn't want to disturb the tadpoles....
Sadly, the raccoons have ripped Helvola, Joanne Pring and Chrysantha to shreds. This pond is so shallow that the coons climb right in. They only reach in the others.....
I do have a small Helvola for you, Bonnie, I potted up the pieces of the rhizome that they shredded. I've got one for me too, waiting for DH to finish a cover.