What can I use as a bowl for a DIY fire bowl/pit?
I have played with various fire pit options in my backyard for 15 years.  I have tons and tons of trees and yard waste and try to burn most or turn it into compost.  I have grabbed the saucers from trash piles and used those - can't put much on there and wind blows stuff off easy.  I have had an enclosed mini-chimney pit I built from stones.  This worked great but was harder to clean and I had to break down the wood into pretty small pieces.

So I have happily moved on to an in ground pit.  I dug my pit down about three feet into the ground about four feet long by two feet wide.   There is one row of stones below ground level and two rows above ground.  It was made from neighbors throw away stones - and the neighbors throw their wood in the pit.  It is safe, looks good, and I just shovel it out every 3 months.  



The example above is pretty close to what I have done except:


Mine is longer going left to right
I have one brick removed on the right so that I can get in and out or prop something up without knocking over bricks.  So it is more of a horse shoe.
My pit goes about a foot above ground.  This is so that ashes don't hit grass directly and so that someone can't just walk into it (we are picky about which limbs we burn).