Drive a wooden stake into the ground to mark each corner of the floor. Connect each stake with a string to create an outline for your dirt concrete floor.
Wet the area within the confines of the string with a garden hose. This will soften the ground and make it easier to work.
Level the ground with a shovel and a garden rake. Remove any high spots, moving the dirt to fill in any low spots. If necessary, fill in any holes with stone then add dirt. When completed, the ground should be level.
Mix dirt and ash into a wheelbarrow in a 2:1 ratio then add water. Mix with a trowel and keep adding water until you have a thick paste.
Spread the mixture over the marked off area with a trowel until you have a level ½-inch layer. Allow at least 48 hours' drying time.
Mix dirt and ash in the wheelbarrow but this time reverse the ratio and add more ash than dirt. Forgo using water and use boiled linseed oil instead. Mix until you have a thick paste.
Mix the dirt/ash combination with sand in a 4:1 ratio: for every 4 parts of dirt/ash, add 1 part sand. Again, keep a thick paste consistency by adding boiled linseed oil as needed. You can also add chopped up hay straw to the mixture to mimic adobe stone. There is no exact ratio for the straw. Simply add in a small amount for additional texture. A good rule of thumb is: 1 cup of straw for each part of dirt/ash.
Spread the mixture over the marked off area with a trowel until you have a level ½-inch layer.
Scribe indentations in the top of the mixture to mimic tiles. An easy way to do this is to draw the thin edge of a ¼-inch board across the surface in a checkered pattern. Allow at least 48 hours' drying time before walking on your dirt cement floor.