As a mouse, you start on the hole. You can wait for the shaman to build a ramp to help you get across, or you can jump to the cheese and wait for the shaman to build a way back. The mice cannot finish this map without the shaman's help.
It is possible to jump straight to the bottom with an air jump, bypassing the middle altogether. It is also possible to corner jump the middle block with the cheese to go to the hole.
As the shaman, you spawn on the hole with the mice. Using a levered ramp is a quick way to get the mice directly from the bottom area straight to the hole at the top.
Alternately, you can build a bridge at either side of the log, although it is recommended to build it at the left side, as it is easier for the mice.