Gravel on the bottom is important. Drainage.

I saw a right neat idea on a Primos video... they were hunting out of dug in 55 gallon steel drums. I guess if you had a big enough tractor with a big enough soil auger it would be a piece of cake. Of course, if you are built like I am (6'0" 165#) its great. If you are like my best friend is (6'1" 285#) then its a bit of a tight fit.

There are several pre-fab/pre-made blinds out of fiberglass/plastic and composite that will last you a LONG time.