I made a small bog for my nephew several years ago. I used a large ruber-maid type container. It is now cracking due to age. I placed about 12 inches of pure river sand in the bottom and then put in about 12 more inches of 2 parts peat and 1 part river sand. *I drilled some small holes about soil level to take care of any excess water. This is the same type set-up that I used on my bog, except mine is deeper and is about 8-9 feet square. I did not put any intentional drain holes in my bog and I have not had any problems. The base of river sand works as a aquifer to hold the water.