I don't know the current situation, but for a long time in many states, you were required by law to buy a commercial casket from a mortician. No homemade or store bought caskets were allowed. The morticians said that was to protect families from 'low quality' caskets. Instead, they paid $2000 or more for their 'high' quality. What changed some minds was when, during a funeral, the pall bearers carrying one of those 'quality' caskets were going down a church steps and the bottom fell out, dumping the body on the steps. I saw the video of that escapade.
For a homemade casket, it doesn't take much of a woodworker to build one with a sturdy enough bottom to hold a body.
