There is nothing you can do until the Shaman starts building.
This map is easiest in normal or hard mode. The divine mode solution will only work if mice come down to the shamans' starting place. Beware that the other shaman may try to sabatoge your design, if behavior like that happens, it might be best to kill them so your build doesn't fall apart.
Some mice may try to wall jump the other side of your hole, to the opposite hole, you can choose to either put a plank below them or block the hole.