about a cylinder of bread-- two easy solutions
1 bread rise in the pan and fills it.. but as it bakes, it shrinks slightly so hot from the oven, bread falls out of the pan (and they did have butter, and lard and tallow to grease the pans to make is all the easier.)
2 even today, bread is sometime baked in hinged or covered pans-- think of fancy 'sandwich' bread that has four flat edges, not the normally rounded top of a loaf-- a cover pan! so for perfect round slices, a hinged pan, each half, a half circle. the bottom half with some feet to stand it upright.
but i think neither meathod was used. i suspect you saw a perfectly round loaf, (about 1/2 lb. in size) with the top cut off, leaving the base and a circular crust.
in some fancy places about, you can get soup served in a hollowed out loaf. a small loaf/ large roll, has its top cut off, most of the interier dough is removed. the bread bowl is baked again, to toast the interior, and then it is filled with soup ($8.95 for a serving!) the side wall hold up and even taste good, since the are soupy-- but the bottom is to over cooked, and hard to eat.
the old fort in Halifax, NS (canada) has a "life in the 1700" tour, including a loaf of bread --the kind that was used as ration for the common soldiers.. these are the same, 1/2 lb round loaves.
accourding to the tour guide, the bread was only baked twice a week, so at some point it was 3 days stale.
the common thing to do, was to use the base (the harded part of the crust) as plate-- to sop up cooking liquid, and to soften the bread.. just like the bread & soup i've had.
with a hard enough crust, even a flat slice (the bottom of the loaf) would be able to sop up all the liquid from a soup/chowder, and leave all the solid bits on top. the whole thing would have been edible.
