My scout troop uses metal garbage can lids propped up on rocks or dirt as well as the cut-down drums. If you use rocks, it still scorches the ground, as does the cut-down 55-gal drum. Another option is a piece of Forest Service fire shelter over a pile of dirt. The shelter protects the inderlying earth/loam/sticks from catching fire and smouldering under the ground and flaring up after you leave.
I prefer to cut out and save the sod and then build the fire on the ground. The biggest mistake I see people making is that they dig their fire pits too deep. This tends to make the fire burn poorly as the base can't get enough air. And forget the rocks, they look "romantic", but then you have ugly, scorched rocks to contend with. The only time we use rocks is in an established fire ring.
One last note, DEAD OUT before you leave.