Having no appropriate place a this time for a large bog garden, I've opted to do two smaller versions. Both of these can be lifted and stored in the greenhouse if necessary over the winter.
Here's the process I used for these gardens.
I had this liner from the pond section at the local hardware store. I bought this last year for something, can't remember what, and it was taking up room in the greenhouse. I used my root knife to puncture the bottom several times for slow drainage.