What have done towards your prep?

[Mortblanc]

Just the normal common sense stuff SS.

8x10 is a BIG cellar. You might consider two smaller units.

Use the north slope of a hill. Keep the berm in the shadows. Definitely not the south or west slope.

Dig deep, you are recreating a cave. It takes a good bit of dirt to recreate being underground. In my area we have a one meter frost line. Less cover than that is subject to outside temp variations. If you pile a meter of dirt top and sides you should reach stability. The frost line in your area is the goal for depth of dirt.

Slope the floor to the door so that it will be self draining. If you have ground water it is likely that in wet weather there would be seepage.

So dig deep, build your cinder block walls, waterproof on the outside. Back fill with coarse gravel for drainage and cover with the dirt you removed for the excavation.

8x10 is a pretty big span for a home built concrete roof, you will need pillars or rebar or both and you are going to have a heavy load with a meter of dirt on top. That is why I suggested two small units rather than one large one.

It might also be easier to talk a neighbor with a small JCB to dig a 2 meter wide slot trench now and another latter rather than come over and dig a huge pit for two days.