they do like to curl! even held in position like this after a week theres a slight curling in of those butted edges.
so, before i sew one up, I'll soak the butted edge in a pan of shallow water till its soft, then clamp the daylights out of it till it dries
so, its good to leave the boards (inside) so they extend past the bark for clamping.
heck , i don't know! :)I've never made one of these before! but i have done other bark work and know what it can do as it dries.
Dried bark, even stored curled up, CAN be rehydrated and can become as flexible as when green...i just use a stock tank.