Shortly after Gaining the translocator gun You come across two locked doors opened with two separate pressure pads. To enter the area you shoot your translocator ball at the door and stand on the pressure pads to open the doors for it.
Similar to Cave flies, you need to move a bunch of flies through flowing lava with your force beam and then next to an amber wall to melt it.
If your facing the door you came in the flies should be to the left of you.
You will First need to place a translocator ball into a small green ring to start lava flowing through a pipe and then shoot your gun through the lava to melt the nearby amber walls. (the wall for the achievement is further around the corner and out of reach of the lava)