I stopped using a trivet for Cobb style bread and rolls quite some time ago.  What I do these days is sprinkle a handful of flour over the base of the oven and put the dough straight on it.

For breads, bread rolls and dampers we also flour the bottom of the oven and place the dough straight on that.

Jeff

Trivets are useful in all sorts of ways , depending on how you use them, Ive always used them under roast meats , never use them when cooking breads dampers or rolls, sometimes use them to get dishes up off the bottom when cooking different sorts of desserts and when cooking some sorts of cakes in cake tins.......use common sense and find what works best for you.
An example would be , if you start to get a build up of moisture on the bottom of a camp oven when roasting meat you will end up with steamed meat, steamed meat isn't roast meat. A trivet will let you add a heap more heat to the bottom of the oven to evaporate  that moisture away, without burning hell out of the roast.
Try doing that with a bed of onion rings under the meat as some folk say is best.

Have a look up top second line Heat Bead Calculator, also a link to a page. Have a read cheers Rober5