As you encounter the ice monster the first time, you run into the first building on the left. There you climb a ledge and run upwards that ramp until you see that stone block you talked about.
Is this where you are?
If so, you must pull this stone out of its niche completely. This will also hide you from the ice monster. Then, if you turn 180 degrees you will find a ramp where you can slide downwards to the exit of the building.
If you don't pull the stone it will block you way afterwards.