How to earn the Ashes in the Maw Achievement in The Hideaway DLC.
Ashes in the Maw Completion Guide
All you need to do is throw the nome statue into the engine/furnace thing in the middle of the level.
start the chapter normally, and once you get to the Big engine/furnace area, turn it on and wait for the nomes to fuel it up as usual. when the ladder on the left side of the area extends, climb it and proceed with that half of the level normally.
Once you get to the janitor's workshop, the nome statue should be on the workbench next to the table saw. Go into the next room, turn on the power, and when he comes in, sneak into the previous room, turn on the table saw, GRAB THE NOME, and run back into the other room, placing it beside the door-thing, then do it again, distracting him with the table saw, only this time, open the hatch, throw the nome statue in, and jump in after it.
Proceed with the level as normal from here, but MAKE SURE YOU DO NOT DIE. once you break down the door with the cart full of coal, carry the nome statue into the room and place it on the hatch.
Next, go out of the room, back into the engine room, and then down into the room beneath the hatch. when you pull the handle, the nomes and the statue should fall through.
Finally, carry the statue up the ramp in the engine room, and throw it into the engine/furnace. Now the achievement should unlock.