I seen an ole timer once that had a 7 foot piece of steel pipe had the ends threaded with some caps screwed on there with a slot cut down the length big enough to get the board in there. Then placed it over a long narrow fire supported on the ends by tripods made from rebar. He made rocking chairs and other furniture. Same principle, may be the cheapest and most importantly the safest way to accomplish your goal. He done it that way for years.