Kuchin in the ground. There used to be a method of kevura in kuchin, which are spaces in a cave’s wall or in the ground, into which a meis is placed from the side. Then, the opening is sealed. When the kuch is dug into the ground for the purpose of burial, it is considered burial in the ground. This was common a long time ago, as is clear from the Gemara (ב''ב דף ק' ע''ב ).
Concrete shelves. There are burial kuchin made from concrete, or even worse, Styrofoam, sometimes without a bottom, sometimes with. They are divided into rows upon rows of burial cells. Then they are overlaid with wall covering stones. In order for it to involve dirt, they put bags of dirt in the cell opening which, over time, spill over the meis, making it like it is buried in dirt. This method is also considered burial in an עציץ since it is not actually in the ground, as above, and the poskim also oppose this method.
