Starting 3 years ago I dug a hole about 16" deep 7' long by ~5' wide.
I went to Lowe's and bought pond liner probably about 10' by 10'. If your lucky you can find one that has been returned and usually they will knock $20 off the price. This size pond liner is normal $40. If you want a bigger bog you can spend more on bigger pond liner. I've heard you can get other cheaper plastics at lowes but I like the expensive stuff because I trust it will last.
1. I dig approximately 16" deep and whatever size I need at the time depending on my budget.
2. Put in the liner
3. Then I use some course sand also found at lowes for installing patio stone; spread it as flat as possible across the ground along the flattended edges of the future bog.
4. After placing the pond liner in the ground but before placing the stone I punch holes (maybe a hole every 2' or so) with a knife or screw driver in the pond liner approximately 4" down from the ground surface or 12 to 14" up from the bottom of the hole.
5. I then start situating the stone over in place.
6. I tuck the remaining pond liner under either the bottom layer of the stone and the ground or the two layers of stone depending on where you have more left over.
7. After the stone is set the way you want it, take a razor blade or knife and cut what little left over pond liner you have away. This way you don't have to look at ugly plastic sticking out the sides.
8. I bug bails of Canadian sphagnum peat moss from lowes or wherever and sand from pool supply stores. They sale me I think 50 lb bags of sand. I used to use play sand but pool sand is better and worth being more expensive to me.
9. I begin adding a bag of sand for every two bails of peat.
10. With a rake or shovel begin mixing the media without puncturing the pond liner.
11. I like to use rain barrels and begin wetting the mix.
12. Be patient; give the media some time to moisten up.
13. Pray for rain.
14. Enjoy the colors and playing bumble bee.
15. Oh yeah, if you have a dog that digs tunnels for a living you can easily loop the bog in with the underground fence.
I've wondered if I have the only electrically wired carnivorous plant bog?
I started small and added on sections at a time to the bog in the above photos. This was 3 years ago.
Se how the pond liner is tucked in the stone.
Outcome
Over years I have just opened up one end of the original and dug a new hole followed by additions of more pond liners. This photo was taken Spring 2010.
I suppose you could use treated wood also similar to what Buckner does on here. Look up some of his threads if you get a chance. He's got awesome bogs.
I was a student of Dr. Mellichamp at UNC Charlotte. His technique and love for Sarracenia inspired me. I got the idea from their bogs and also the bogs at UNC Chapel Hill although theirs are better built. Building these can be labor intensive. The more time the better the outcome.
You should visit there if your ever the NC way.
Here is a photo of one at UNC Charlotte. They have several like this.