- climb block with one Lemming
- dig through from other side
- separate 1 Lemming to build bridges with 1 blocker
- first bridge over small hump
- second bridge right before Lemming falls over the bottom edge
- two bridges over large gap
- one bridge over small gap (one out of six should be spare, but you can use it for the large gap perhaps)
- blow up blocker and bring them home