I've been baking a lot of boules and larger (~1 kg) long hearth loaves, and want them to rise higher and spread less. I can't seem to get a loaf more than about 2 inches high.
I proof them in makeshift bannettons (tightly woven long sisal baskets) and the dough is wrapped in heavily floured linen. When I turn them over on the peel, they flatten out a bit, and then flatten more when I slash the tops.
In my last round with the oven, I made one larger long loaf, which I slashed before putting in the oven, and two smaller boules, which I accidentally put in the oven without slashing, so pulled them out to slash after giving them about 5 minutes for their bottoms to set. The boules sprang higher, but I'd still like to see more..