Building a Yurt Platform with Earth Bags, Skoria, and Concrete

Can one build a simple platform with earth bags filling them with skoria while not using portland cement?

I know that I must dig a rubble trench, tossing the dirt just outside the trench so that I can berm the sides of the platform.
I know I must fill said trench with skoria.
I know that I must fill the first couple rounds of earth bags with skoria <- It is at this step that I don't know if the earth bags require a skoria + cement mixture or just skoria.
I know that I must fill in the space contained within the earth bags with skoria acting as insulation.
I know that I must lay out plastic sheeting atop the skoria to prevent the wet concrete from leaking downward, then pour cement inside of my formwork.

Are these pretty much the steps I need to take? I'm unsure of whether or not portland cement is needed for any kind of earth bag fill or just if you're using actual sifted dirt and rock.
The platform is only going to be about 12" high plus the height of a concrete slab poured atop it. It is upon that concrete slab that I will build my yurt.

Sounds like a good project.
A couple of points;
- where is the design coming from?
- earthbags filled with scoria are not much good unless contained within the trench, because if the bags degrade, split the scoria may dribble out.
- scoria is too course to mix with portland cement [ the fine dusty stuff], it would need sand as well to form any strong material.
- you mention wet concrete, cement mixture and cement almost as if they are the same material, is that correct. Because they are all different and are used differently.
Often you would use bigger rocks, 100-250mm diameter on top of the loose scoria, with the rocks mortared [ sand / cement mix] together, to form a wall as high as you need and about12- 18 inches wide.
That rock wall would then be filled with sand  etc to create a base for the concrete slab which would also sit on the rock wall at the edges..

Thank you for the speedy reply. The plans actually came from this forum. I don't have the link, but I attached the pdf. The plans are a little sparce on detail, but I think you just filled in some of it.

When I said skoria + cement mixture, I meant portland cement plus skoria mixed together, but from what you told me, I need to add some sifted sand to that? We're in Taos, New Mexico where I hope the dirt will be okay for that. Its very sandy on top with heavier clay particles a little ways down.

The concrete is just going to be for the slab on top. I mentioned "wet concrete" because I thought all concrete starts out wet and then dries. I don't know anything about concrete or cement at all. I've never worked with it. A fellow who does work with concrete is going to meet me out at the build site and rent out his mixer to me. I'm relying pretty heaviily on his expertise because I'm totally out of my depth on how to build a circular formwork. Even the plans provided don't go in to great detail on that. I think they just kind of assume it is easy enough to figure out, but It is actually really stressing me out.

I read that link and the other listed in it.
I have seen them elsewhere and they are ok.
Do you get rain where you are? This design is for low rainfall areas.
I would consider a change or two;
- scoria is used in the bags as insulation, unless you get frozen ground down 2-4 ft I would not use it in the bags.
- I would use an earth mix as detailed in Earth bag construction. You need a sand, clay mix that hardens when it dries out.
Foundation would be as follows;
- place a pole in the ground at the centre of your circle, attach ring over the pole and attach a string to the ring.
- this is your radius gauge which you will use 100's of times to check the dimension to the outer side of the circle.
- trench 8 inches deep and 4 inches wider than your earthbags when they are filled.
- rubble or scoria tamped into the trench with a square tamper.
- earthbags, tamped as detailed with earthbag construction techniques, two or three layers high with barbed wire between each course to hold the bags together.
- fill the volume created between the natural soil and the top of the earthbags, scoria is good since it will not draw moisture up, but if you use a plastic sheet over the soil, any fill will be ok.
CONCRETE
- form the circular formwork but using T posts driven into the ground and flexible plywood and checking with your radius string its in line.
- I would install the posts, checking each time with the string and then fit the plywood inside, making sure the top edge is level all around, screw the wood to the posts from the outside.
- Then strengthen the posts so they are not pushed over by the wet concrete.
- if ready mix concrete was available it is worth checking its cost, sometimes it better value than mixing batches.
- if batching your own concrete, I would lay it in small areas creeping around as the brews are mixed.
- I would use 50 mm of concrete, but check what others recommend.

Have you considered an earth floor, you need a good clay mix though.

Where we're at in New Mexico, rainfall is very scarce. There is a wet season, but overall the place only gets about 1ft of rainfall a year. During the coldest parts of the year, ground freezes down to a depth of 2ft.
There is plenty of sand, clay, and rock where we're building, so I guess that earthbag mix is the way to go. Months ago, I was surfing the web and found some great instructions that even mentioned the dimensions of the filled earthbags, but I can't find where that was. I suspect they were on the permies forum somewhere, but I'm not sure. If that rings a bell to you, let me know.

If you have plenty of rocks, I would not bother with the earth bags.
Just build a wall with the rocks and mortar them together.
Its almost like brick laying.
Your foundation may need to go past the frost zone, that is something I am not familiar with yet, since we dont have that issue in 'stralia' !
What are planning for water etc?