The pyramids in Egypt were made out of mostly sand mixed with mud. And they've stood for 7000 years. You don't even need to bake the bricks, you just have to mix the sand with clay/earth and water, and some dry hay or grass if you can. And make sure they are dried out. Good luck
Not sandstone but calcium carbonate (limestone). Outer casings were polished limestone.the bricks in the pyramids were made by nature not man, they carved huge blocks of sandstone out of the bedrock. that's even more labor intensive then firing bricks.