Step 6: Producing the first-2nd floor transition and closing up the back.
After this is done, cut steps into the roof as shown in the photos (this will suck if you have a crap shovel, you need something made of steel. You can use a hammer and chisel if you are having trouble)
Once this is done, build 2 more arches. These have to be 2 floors high so that you are able to fully stand up inside. That means 6 block high walls instead of just 3 as in the previous step.
After all that is done. Close the back up by making a simple wall.
REMINDER: Remember to fill up all the gaps with slop (Wet snow)